Chapter 3

Multiplication Concepts and Fact Fluency

Multiplication as Equal Groups

Multiplication as Equal Groups

Multiplication helps us count equal groups quickly. Equal groups means each group has the same number of items.

For example, if there are 3 baskets and each basket has 4 apples, we can count by adding: 4 + 4 + 4. Multiplication is a faster way to show this.

We write:

$$3 \times 4 = 12$$

This means 3 groups of 4 make 12 altogether.

In multiplication:

  • The first factor tells how many groups there are.
  • The second factor tells how many are in each group.
  • The product is the total number of items.

So in \(3 \times 4 = 12\):

  • 3 = number of groups
  • 4 = number in each group
  • 12 = total

A good way to think about multiplication is:

$$\text{number of groups} \times \text{number in each group} = \text{total}$$

You can also solve multiplication by using repeated addition. If there are 5 groups of 2, then:

$$2 + 2 + 2 + 2 + 2 = 10$$

So:

$$5 \times 2 = 10$$

This is why multiplication and repeated addition are connected. Multiplication is a shortcut for adding the same number again and again.

How to Understand Equal Groups

  1. Find out how many groups there are.
  2. Find out how many items are in each group.
  3. Multiply to find the total.

You can model equal groups with drawings, counters, or objects. If you draw 4 circles and put 3 dots in each circle, that shows 4 equal groups of 3.

Then the multiplication sentence is:

$$4 \times 3 = 12$$

Worked Example 1

There are 2 bags. Each bag has 5 marbles. How many marbles are there in all?

Step 1: Number of groups = 2 bags

Step 2: Number in each group = 5 marbles

Step 3: Multiply

$$2 \times 5 = 10$$

Answer: There are 10 marbles in all.

You can also check with addition:

$$5 + 5 = 10$$

Worked Example 2

There are 4 plates. Each plate has 3 cookies. How many cookies are there altogether?

Step 1: Number of groups = 4 plates

Step 2: Number in each group = 3 cookies

Step 3: Multiply

$$4 \times 3 = 12$$

Answer: There are 12 cookies altogether.

Check with repeated addition:

$$3 + 3 + 3 + 3 = 12$$

Worked Example 3

A teacher makes 6 equal groups of pencils. There are 4 pencils in each group. How many pencils are there in all?

Step 1: Number of groups = 6

Step 2: Number in each group = 4

Step 3: Multiply

$$6 \times 4 = 24$$

Answer: There are 24 pencils in all.

Check with addition:

$$4 + 4 + 4 + 4 + 4 + 4 = 24$$

Worked Example 4

There are 7 boxes. Each box has 8 crayons. How many crayons are there in all?

Step 1: Number of groups = 7

Step 2: Number in each group = 8

Step 3: Multiply

$$7 \times 8 = 56$$

Answer: There are 56 crayons in all.

Check with repeated addition:

$$8 + 8 + 8 + 8 + 8 + 8 + 8 = 56$$

Important Idea

When you see multiplication as equal groups, always ask:

  • How many groups are there?
  • How many are in each group?
  • What is the total?

This helps you understand word problems and write the correct multiplication sentence.

Watch Out!

  • Equal groups must have the same number in each group.
  • If the groups have different numbers, it is not a multiplication equal-groups model.
  • The product tells the total number of all items together.

For example, 3 groups with 2, 4, and 5 items are not equal groups. Multiplication as equal groups only works when every group matches.

Try Thinking This Way

If you hear “5 groups of 6,” think:

$$5 \times 6$$

That means 5 equal groups, with 6 in each group.

If you hear “3 groups of 9,” think:

$$3 \times 9$$

The more you practice seeing groups, the easier multiplication facts become.

Summary

Multiplication shows the total in equal groups. The first factor tells the number of groups, and the second factor tells how many are in each group. You can use repeated addition to check your answer, but multiplication is the faster way to find the total.

Put what you read to the test

You've worked through Multiplication as Equal Groups. Try answering a few questions to see what stuck — and what might deserve a quick reread before you move on.

Multiplication as Arrays and Area

Multiplication as Arrays and Area

Multiplication helps us count equal groups quickly. Two important ways to understand multiplication are with arrays and area.

An array is a set of objects arranged in rows and columns. A row goes across. A column goes up and down.

When we use arrays, multiplication shows how many objects are in all. For example, 3 rows of 4 means there are 3 groups, and each group has 4 objects.

We write that as \(3 \times 4\). This means:

  • 3 rows of 4, or
  • 4 columns of 3

Both ways count the same total.

Area is the amount of space inside a flat shape. When we find the area of a rectangle, we count how many square units fit inside it.

A square unit is a little square that measures 1 unit by 1 unit. If a rectangle has 4 rows of square units and 6 columns of square units, then it has \(4 \times 6 = 24\) square units.

This is why arrays and area are connected. A rectangle made of square units is really an array of squares.

Main Idea 1: Multiplication as Rows and Columns

To read an array, count the number of rows and the number of columns.

  • The first factor can tell the number of rows.
  • The second factor can tell the number of objects in each row, or the number of columns.

So if an array has 5 rows and 3 columns, we can write:

$$5 \times 3 = 15$$

That means there are 15 objects in all.

Main Idea 2: Turn Repeated Addition into Multiplication

Arrays help us see repeated addition. If there are 4 rows with 2 objects in each row, we could add:

$$2 + 2 + 2 + 2 = 8$$

That is the same as:

$$4 \times 2 = 8$$

Multiplication is faster than adding the same number again and again.

Main Idea 3: Multiplication Can Be Shown More Than One Way

If you turn an array, the total does not change. For example:

$$3 \times 5 = 15$$

and

$$5 \times 3 = 15$$

One array might show 3 rows of 5. Another might show 5 rows of 3. The arrays look different, but both have 15 objects.

Main Idea 4: Area of a Rectangle

To find the area of a rectangle, multiply the side lengths if they are whole numbers.

If a rectangle is 7 units long and 2 units wide, then the area is:

$$7 \times 2 = 14$$

The answer is 14 square units.

We say square units because area counts squares that cover the inside of the rectangle.

How Arrays and Area Match

Imagine drawing a rectangle on grid paper. If it covers 3 rows and 4 columns of little squares, then:

  • the array is 3 by 4, and
  • the area is 12 square units

We can write:

$$3 \times 4 = 12$$

The multiplication equation tells both the number of squares in the array and the area of the rectangle.

Worked Example 1: A Simple Array

A student arranges counters in 2 rows of 6.

Step 1: Count the rows: 2

Step 2: Count how many in each row: 6

Step 3: Write the multiplication equation:

$$2 \times 6 = 12$$

So there are 12 counters in all.

Worked Example 2: Repeated Addition to Multiplication

An array has 4 rows with 3 stars in each row.

You could add:

$$3 + 3 + 3 + 3 = 12$$

Or you can multiply:

$$4 \times 3 = 12$$

So the array has 12 stars.

Worked Example 3: Finding Area with Square Units

A rectangle is 5 units long and 4 units wide.

Step 1: Think of the rectangle as 5 columns and 4 rows of squares.

Step 2: Multiply:

$$5 \times 4 = 20$$

The area is 20 square units.

Worked Example 4: A Bigger Rectangle

A garden is shaped like a rectangle. It is 8 units long and 3 units wide. What is its area?

Step 1: Use multiplication for area.

$$8 \times 3 = 24$$

Step 2: Write the unit.

The area is 24 square units.

This also means the garden could be shown as an array with 8 rows of 3 or 3 rows of 8.

Tips for Solving Problems

  • Count rows carefully.
  • Count columns carefully.
  • Multiply rows by columns to find the total.
  • For area, remember to say square units.
  • If you get stuck, use repeated addition first.

Common Mistakes to Watch For

  • Mixing up rows and columns.
  • Counting only one row instead of all rows.
  • Forgetting the word square when naming area units.
  • Adding side lengths instead of multiplying them when finding area.

Let’s Review

Arrays show multiplication with rows and columns. Area shows multiplication by counting square units inside a rectangle.

When you see a rectangle on grid paper, you can think of it as an array of squares. Multiply the number of rows by the number of columns to find how many squares there are.

That is why multiplication as arrays and multiplication as area are closely connected.

Put what you read to the test

You've worked through Multiplication as Arrays and Area. Try answering a few questions to see what stuck — and what might deserve a quick reread before you move on.

Multiplicative Comparison Concept

Multiplicative Comparison Concept

Sometimes in math, we compare two amounts by asking how many times as many one amount is as another amount.

This is called a multiplicative comparison. It means we use multiplication to compare. We are not just finding how much more. We are finding how many times bigger or smaller one amount is.

For example, if Mia has 3 stickers and Ben has 12 stickers, Ben does not just have 9 more stickers. Ben has 4 times as many stickers as Mia because $$3 \times 4 = 12$$

That idea of times as many is the heart of multiplicative comparison.

Important words to know

  • times as many — compares one amount to another using multiplication
  • times as much — compares amounts like money, water, or weight
  • times as long, times as heavy, times as old — all of these use multiplication to compare

Additive comparison and multiplicative comparison are different.

An additive comparison tells how many more or how many fewer.

A multiplicative comparison tells how many times as many or how many times as much.

Look at this example:

  • Lena has 4 apples.
  • Omar has 12 apples.

We can compare these numbers in two different ways:

  • Additive comparison: Omar has 8 more apples than Lena.
  • Multiplicative comparison: Omar has 3 times as many apples as Lena.

Both statements are true, but they mean different things.

How to understand “times as many”

If one group has 2 items, then:

  • 2 times as many means 4
  • 3 times as many means 6
  • 4 times as many means 8

We can write this with multiplication:

$$2 \times 3 = 6$$

So 6 is 3 times as many as 2.

You can think of it as making equal groups of the smaller amount.

If a toy car costs \(5\) dollars and a big toy truck costs \(4\) times as much, then we make 4 groups of 5:

$$5 + 5 + 5 + 5 = 20$$

So the truck costs $$5 \times 4 = 20$$ dollars.

A helpful pattern

When you hear:

  • 3 times as many as 6, think \(6 \times 3\)
  • 5 times as heavy as 2, think \(2 \times 5\)
  • 4 times as long as 7, think \(7 \times 4\)

The number after “as” is the starting amount. The phrase “times” tells how many groups of that amount to make.

Worked Example 1

Sara has 4 books. Tom has 3 times as many books as Sara. How many books does Tom have?

Step 1: Find the starting amount. Sara has \(4\) books.

Step 2: Tom has \(3\) times as many, so multiply.

$$4 \times 3 = 12$$

Answer: Tom has 12 books.

Worked Example 2

A baby rabbit weighs 2 pounds. A large rabbit weighs 5 times as much. How much does the large rabbit weigh?

Step 1: Start with the baby rabbit’s weight, \(2\) pounds.

Step 2: Multiply by 5.

$$2 \times 5 = 10$$

Answer: The large rabbit weighs 10 pounds.

Worked Example 3

Jay drew 6 stars. Kim drew 24 stars. How many times as many stars did Kim draw as Jay?

Here, we know both amounts. We need to find the comparison.

Ask: \(6\) times what number equals \(24\)?

$$6 \times 4 = 24$$

Answer: Kim drew 4 times as many stars as Jay.

Worked Example 4

A red ribbon is 3 inches long. A blue ribbon is 4 times as long as the red ribbon. A green ribbon is 2 times as long as the blue ribbon. How long is the green ribbon?

Step 1: Find the blue ribbon.

$$3 \times 4 = 12$$

The blue ribbon is \(12\) inches long.

Step 2: Find the green ribbon.

$$12 \times 2 = 24$$

Answer: The green ribbon is 24 inches long.

How to solve multiplicative comparison word problems

  1. Read the problem carefully.
  2. Find the starting amount.
  3. Look for words like times as many, times as much, or times as long.
  4. Multiply to find the new amount, or think about what number makes the multiplication sentence true.
  5. Check if your answer makes sense.

Tips to help you

  • If the problem says times as many, think multiply.
  • If one amount is bigger because it is “4 times as many,” the answer should be larger than the starting amount.
  • If you know both amounts, ask: How many groups of the smaller amount make the larger amount?
  • You can use repeated addition to check your multiplication.

Let’s compare two statements

Suppose Noah has 5 marbles and Eva has 15 marbles.

  • Noah has 10 fewer marbles than Eva.
  • Eva has 3 times as many marbles as Noah.

The first statement uses subtraction. The second statement uses multiplication. When you see times as many, you are using multiplicative comparison.

Quick practice thinking

  • 8 is 2 times as many as 4 because \(4 \times 2 = 8\)
  • 18 is 3 times as many as 6 because \(6 \times 3 = 18\)
  • 20 is 5 times as much as 4 because \(4 \times 5 = 20\)

Summary

Multiplicative comparison means comparing amounts by using multiplication.

Words like times as many, times as much, and times as long tell us to think about equal groups and multiplication.

To solve these problems, find the starting amount and multiply by the comparison number. If both amounts are given, figure out how many times the smaller amount fits into the larger amount.

Put what you read to the test

You've worked through Multiplicative Comparison Concept. Try answering a few questions to see what stuck — and what might deserve a quick reread before you move on.

Multiplication by Zero and One

Multiplication by Zero and One

Today we will learn a very important multiplication idea: what happens when you multiply by 0 and what happens when you multiply by 1.

These two facts are special because they follow simple rules every time. When you know these rules, you can solve multiplication problems faster and with more confidence.

What does multiplication mean?

Multiplication can mean equal groups. For example, \(3 \times 4\) means 3 groups of 4.

It can also mean repeated addition:

$$3 \times 4 = 4 + 4 + 4 = 12$$

Now let’s see what happens when one of the numbers is 0 or 1.

Multiplying by 1

When you multiply any number by 1, the number stays the same.

This is called the Identity Property of Multiplication. A simpler way to remember it is: Multiplying by 1 does not change a number.

Examples:

  • \(7 \times 1 = 7\)
  • \(1 \times 12 = 12\)
  • \(25 \times 1 = 25\)

Why does this happen?

Think about equal groups. If you have 1 group of 8, you have 8 total.

$$1 \times 8 = 8$$

If you have 6 groups of 1, you have 6 total.

$$6 \times 1 = 6$$

So multiplying by 1 keeps the number the same.

Multiplying by 0

When you multiply any number by 0, the product is always 0.

This is called the Zero Property of Multiplication. A simple way to remember it is: Any number times 0 equals 0.

Examples:

  • \(9 \times 0 = 0\)
  • \(0 \times 15 = 0\)
  • \(100 \times 0 = 0\)

Why does this happen?

Think about equal groups again. If you have 4 groups of 0 apples, each group has nothing in it. So there are 0 apples total.

$$4 \times 0 = 0 + 0 + 0 + 0 = 0$$

If you have 0 groups of 5, there are no groups at all, so there is still nothing to count.

$$0 \times 5 = 0$$

Important rules to remember

  • Any number multiplied by 1 stays the same.
  • Any number multiplied by 0 equals 0.
  • It does not matter which number comes first. For example, \(1 \times 9 = 9\) and \(9 \times 1 = 9\).
  • It also does not matter which number comes first with 0. For example, \(0 \times 6 = 0\) and \(6 \times 0 = 0\).

Worked Example 1

Solve: \(1 \times 14\)

Because multiplying by 1 keeps the number the same, the answer is:

$$1 \times 14 = 14$$

Worked Example 2

Solve: \(8 \times 0\)

Any number multiplied by 0 equals 0, so:

$$8 \times 0 = 0$$

Worked Example 3

Solve: \(0 \times 11\)

There are 0 groups of 11, so there is nothing to count.

$$0 \times 11 = 0$$

Worked Example 4

Solve: \(19 \times 1\)

Multiplying by 1 does not change the number.

$$19 \times 1 = 19$$

How to decide quickly

  1. Look to see if one factor is 0. If yes, the answer is 0.
  2. If not, look to see if one factor is 1. If yes, the answer is the other number.
  3. If there is no 0 or 1, use your other multiplication strategies.

Watch out for this mistake

Sometimes students mix up the rules for 0 and 1.

  • \(6 \times 1 = 6\), not 0
  • \(6 \times 0 = 0\), not 6

A good memory trick is:

  • 1 means keep it.
  • 0 means zero total.

Try thinking about real-life examples

If 1 bag has 7 marbles, then 1 bag of 7 marbles is still 7 marbles.

$$1 \times 7 = 7$$

If 5 bags each have 0 marbles, then there are 0 marbles total.

$$5 \times 0 = 0$$

Summary

Multiplying by 1 keeps a number the same. Multiplying by 0 always gives 0.

These are special multiplication facts that help you solve problems quickly. Remember: by 1, keep the number; by 0, the product is 0.

Put what you read to the test

You've worked through Multiplication by Zero and One. Try answering a few questions to see what stuck — and what might deserve a quick reread before you move on.

Doubling Strategies

Doubling Strategies help us use what we already know about doubles in addition to solve multiplication facts quickly.

A double means adding the same number two times. For example, \(6 + 6 = 12\). This is also the same as multiplying by 2, because \(2 \times 6 = 12\).

In this lesson, you will learn how doubling helps with the 2s, 4s, and 8s facts. When we keep doubling a number, we can find multiplication answers faster and with more confidence.

Think of doubling like making something twice as much. If you double again, you make it twice as much again. This is a great strategy for multiplication.

Step 1: Use doubles for the 2s facts

Multiplying by 2 means making 2 equal groups of a number. That is the same as adding the number to itself.

For example:

  • \(2 \times 3 = 3 + 3 = 6\)
  • \(2 \times 7 = 7 + 7 = 14\)
  • \(2 \times 9 = 9 + 9 = 18\)

So if you know your doubles facts, you already know your 2s multiplication facts.

Step 2: Double again for the 4s facts

Multiplying by 4 means making 4 equal groups. One way to do that is to multiply by 2, and then double the answer.

For example, to find \(4 \times 6\):

  1. First find \(2 \times 6 = 12\).
  2. Then double 12: \(12 + 12 = 24\).

So, $$4 \times 6 = 24$$

This works because 4 is double 2. If you know the 2s fact, you can double it to get the 4s fact.

Step 3: Double again for the 8s facts

Multiplying by 8 means making 8 equal groups. You can get that answer by doubling the 4s fact, or by doubling three times from the starting number.

For example, to find \(8 \times 5\):

  1. Start with \(2 \times 5 = 10\).
  2. Double 10 to get \(4 \times 5 = 20\).
  3. Double 20 to get \(8 \times 5 = 40\).

So, $$8 \times 5 = 40$$

This pattern is very helpful:

  • \(2 \times n\) means double the number
  • \(4 \times n\) means double it again
  • \(8 \times n\) means double it one more time

Worked Example 1

Find \(2 \times 8\).

Use a doubles fact: \(8 + 8 = 16\).

So, $$2 \times 8 = 16$$

Worked Example 2

Find \(4 \times 7\).

First double 7:

\(2 \times 7 = 14\)

Then double 14:

\(14 + 14 = 28\)

So, $$4 \times 7 = 28$$

Worked Example 3

Find \(8 \times 3\).

Double 3 to get 6.

Double 6 to get 12.

Double 12 to get 24.

So, $$8 \times 3 = 24$$

Worked Example 4

Find \(8 \times 6\).

First find the 2s fact:

\(2 \times 6 = 12\)

Then double to get the 4s fact:

\(4 \times 6 = 24\)

Then double again to get the 8s fact:

\(8 \times 6 = 48\)

So, $$8 \times 6 = 48$$

Helpful Tips

  • If you know a doubles addition fact, you know a 2s fact.
  • If you know a 2s fact, double it to get a 4s fact.
  • If you know a 4s fact, double it to get an 8s fact.
  • Say the doubles out loud to help remember them.

Look at the pattern

Let’s use the number 4:

  • \(2 \times 4 = 8\)
  • \(4 \times 4 = 16\)
  • \(8 \times 4 = 32\)

Each answer is doubled from the one before it. This is why the doubling strategy works so well.

When should you use doubling strategies?

  • When you are multiplying by 2, 4, or 8
  • When you know the smaller fact and want to build the bigger fact
  • When you want a fast way to check your answer

Summary

Doubling strategies connect addition doubles and multiplication facts. Multiplying by 2 means double once. Multiplying by 4 means double twice. Multiplying by 8 means double three times.

When you practice doubles facts, you also get stronger at multiplication. That makes solving 2s, 4s, and 8s facts much easier.

Put what you read to the test

You've worked through Doubling Strategies. Try answering a few questions to see what stuck — and what might deserve a quick reread before you move on.

Tripling and Related Facts

Tripling means making a number 3 times as large. If you triple 4, you have 3 groups of 4.

We can write that as \(3 \times 4 = 12\). We can also think of it as adding the same number 3 times: \(4 + 4 + 4 = 12\).

Learning the 3s facts helps us understand the 6s facts and 9s facts too. These facts are related because 6 is double 3, and 9 is triple 3.

When you know one fact, you can often use it to figure out another fact faster.

Main idea 1: Tripling means 3 equal groups.

Multiplication shows equal groups. In a tripling problem, there are always 3 equal groups, or the number is being multiplied by 3.

  • \(3 \times 2\) means 3 groups of 2
  • \(3 \times 5\) means 3 groups of 5
  • \(3 \times 8\) means 3 groups of 8

You can find the answer by skip-counting by 3s or by adding the number 3 times.

For example:

  • \(3 \times 4 = 4 + 4 + 4 = 12\)
  • \(3 \times 7 = 7 + 7 + 7 = 21\)

Main idea 2: The 3s facts follow patterns.

When you multiply by 3, the answers grow by 3 each time.

Look at the pattern:

$$ 3 \times 1 = 3 \\ 3 \times 2 = 6 \\ 3 \times 3 = 9 \\ 3 \times 4 = 12 \\ 3 \times 5 = 15 \\ 3 \times 6 = 18 $$

Each product is 3 more than the one before it.

This helps you solve facts you do not remember right away. If you know \(3 \times 5 = 15\), then \(3 \times 6\) is 3 more, so it is \(18\).

Main idea 3: The 6s facts are related to the 3s facts.

Since 6 is double 3, you can use a 3s fact and double it to get a 6s fact.

For example, if you know:

$$3 \times 4 = 12$$

Then double 12 to get:

$$6 \times 4 = 24$$

This works because 6 groups of 4 is the same as 2 groups of \(3 \times 4\).

More examples:

  • \(3 \times 5 = 15\), so \(6 \times 5 = 30\)
  • \(3 \times 7 = 21\), so \(6 \times 7 = 42\)
  • \(3 \times 9 = 27\), so \(6 \times 9 = 54\)

Main idea 4: The 9s facts are also related to the 3s facts.

Since 9 is 3 groups of 3, you can use a 3s fact and triple it to get a 9s fact.

For example, if you know:

$$3 \times 4 = 12$$

Then triple 12 to get:

$$9 \times 4 = 36$$

You can also think of \(9 \times 4\) as \(3 \times 4 + 3 \times 4 + 3 \times 4\).

$$12 + 12 + 12 = 36$$

More examples:

  • \(3 \times 2 = 6\), so \(9 \times 2 = 18\)
  • \(3 \times 6 = 18\), so \(9 \times 6 = 54\)
  • \(3 \times 8 = 24\), so \(9 \times 8 = 72\)

Main idea 5: You can use related facts to solve multiplication quickly.

Related facts are multiplication facts that help you find other facts. The 3s, 6s, and 9s families are closely connected.

  • To solve a 3s fact, think of 3 equal groups.
  • To solve a 6s fact, solve the 3s fact first and then double.
  • To solve a 9s fact, solve the 3s fact first and then triple.

This is a smart strategy because you do not have to memorize every fact by itself.

Worked Example 1

Find \(3 \times 6\).

Think: 3 groups of 6.

$$6 + 6 + 6 = 18$$

So, \(3 \times 6 = 18\).

Worked Example 2

Find \(6 \times 6\) using a related fact.

First find the 3s fact:

$$3 \times 6 = 18$$

Now double 18:

$$18 + 18 = 36$$

So, \(6 \times 6 = 36\).

Worked Example 3

Find \(9 \times 5\) using a related fact.

First find the 3s fact:

$$3 \times 5 = 15$$

Now triple 15:

$$15 + 15 + 15 = 45$$

So, \(9 \times 5 = 45\).

Worked Example 4

A ribbon is 7 inches long. Mia wants 3 ribbons that are the same length. Then she wants to know how long 6 ribbons would be and how long 9 ribbons would be.

First, find 3 ribbons:

$$3 \times 7 = 21$$

So 3 ribbons are 21 inches long.

Now find 6 ribbons by doubling the 3-ribbon length:

$$21 + 21 = 42$$

So, \(6 \times 7 = 42\).

Now find 9 ribbons by tripling the 3-ribbon length:

$$21 + 21 + 21 = 63$$

So, \(9 \times 7 = 63\).

Helpful tips to remember

  • Tripling means multiply by 3.
  • \(3 \times n\) means 3 equal groups of \(n\).
  • Use repeated addition if needed.
  • Use 3s facts to help with 6s facts by doubling.
  • Use 3s facts to help with 9s facts by tripling.
  • Look for patterns: products in the 3s go up by 3 each time.

Quick fact family connections

$$ 3 \times 4 = 12 $$ $$ 6 \times 4 = 24 \quad \text{(double 12)} $$ $$ 9 \times 4 = 36 \quad \text{(triple 12)} $$

See how one fact can lead to two more facts? That is the power of related facts.

Summary

Tripling means making 3 equal groups, or multiplying by 3. The 3s facts are important because they help you solve 6s facts and 9s facts. If you know a 3s fact, you can double it to find a 6s fact and triple it to find a 9s fact. Looking for patterns and using related facts makes multiplication faster and easier.

Put what you read to the test

You've worked through Tripling and Related Facts. Try answering a few questions to see what stuck — and what might deserve a quick reread before you move on.

Benchmark Facts

Benchmark Facts are multiplication facts you know very well and can use to help solve other facts.

In 4th Grade, the most helpful benchmark facts are usually the 5s facts and the 10s facts. These facts are easy to remember, so they can act like math anchors.

For example, if you know that \(6 \times 10 = 60\), you can use that fact to help solve \(6 \times 9\). If you know that \(7 \times 5 = 35\), you can use that fact to help solve \(7 \times 6\).

Using benchmark facts helps you solve multiplication problems quickly and mentally, without always counting or drawing pictures.

Main Idea: Start with a fact you know, then adjust to find the fact you do not know.

There are two very useful ways to use benchmark facts:

  • Use 10s facts to solve facts close to 10.
  • Use 5s facts to solve facts close to 5.

Using 10s facts

The 10s facts are often easy because you can multiply by 10 by putting a zero at the end of the number.

Some 10s benchmark facts are:

  • \(3 \times 10 = 30\)
  • \(4 \times 10 = 40\)
  • \(8 \times 10 = 80\)
  • \(9 \times 10 = 90\)

If the fact you want is close to a 10s fact, you can subtract a group or add a group.

For example:

  • To find \(6 \times 9\), think: \(6 \times 10 = 60\). But 9 is one less group than 10, so subtract one group of 6. Then \(60 - 6 = 54\).
  • To find \(4 \times 11\), think: \(4 \times 10 = 40\). But 11 is one more group than 10, so add one group of 4. Then \(40 + 4 = 44\).

Using 5s facts

The 5s facts are also helpful because many students know them well. Counting by 5s can help you remember them.

Some 5s benchmark facts are:

  • \(2 \times 5 = 10\)
  • \(6 \times 5 = 30\)
  • \(7 \times 5 = 35\)
  • \(9 \times 5 = 45\)

If the fact you want is close to a 5s fact, you can use the 5s fact and then add or subtract one more group.

For example:

  • To find \(7 \times 6\), think: \(7 \times 5 = 35\). Then add one more group of 7. So \(35 + 7 = 42\).
  • To find \(8 \times 4\), think: \(8 \times 5 = 40\). But 4 is one less group than 5, so subtract one group of 8. Then \(40 - 8 = 32\).

Worked Example 1

Solve \(3 \times 9\) using a benchmark fact.

Use the 10s fact:

$$3 \times 10 = 30$$

But \(9\) is one less than \(10\), so subtract one group of \(3\):

$$30 - 3 = 27$$

So,

$$3 \times 9 = 27$$

Worked Example 2

Solve \(8 \times 6\) using a benchmark fact.

Use the 5s fact:

$$8 \times 5 = 40$$

Now add one more group of \(8\):

$$40 + 8 = 48$$

So,

$$8 \times 6 = 48$$

Worked Example 3

Solve \(4 \times 11\) using a benchmark fact.

Use the 10s fact:

$$4 \times 10 = 40$$

Now add one more group of \(4\):

$$40 + 4 = 44$$

So,

$$4 \times 11 = 44$$

Worked Example 4

Solve \(9 \times 4\) using a benchmark fact.

Use the 5s fact because \(4\) is close to \(5\):

$$9 \times 5 = 45$$

But \(4\) is one less than \(5\), so subtract one group of \(9\):

$$45 - 9 = 36$$

So,

$$9 \times 4 = 36$$

How to choose a benchmark fact

  1. Look at the multiplication fact you need to solve.
  2. Ask yourself: Is it close to 5 or close to 10?
  3. Use the 5s fact or 10s fact you know.
  4. Add one group or subtract one group.
  5. Check if your answer makes sense.

Examples of choosing a benchmark

  • \(7 \times 9\): use \(7 \times 10\), then subtract 7.
  • \(6 \times 4\): use \(6 \times 5\), then subtract 6.
  • \(3 \times 6\): use \(3 \times 5\), then add 3.
  • \(8 \times 11\): use \(8 \times 10\), then add 8.

Why benchmark facts are helpful

  • They make multiplication faster.
  • They help you use facts you already know.
  • They are useful for mental math.
  • They help build fact fluency.

Tips to remember

  • When using a 10s fact, think: one more 10 or one less 10.
  • When using a 5s fact, think: one more 5 or one less 5.
  • When you add or subtract, use the other factor as the group size.

For example, in \(6 \times 9\), you start with \(6 \times 10\). Since one group is removed, you subtract 6, not 9.

That is because there are 10 groups of 6, and then 9 groups of 6. The group size stays the same.

Quick practice to think about

  • \(5 \times 8\): use \(5 \times 10\), then subtract two groups of 5.
  • \(7 \times 4\): use \(7 \times 5\), then subtract one group of 7.
  • \(9 \times 6\): use \(9 \times 5\), then add one group of 9.

Summary

Benchmark facts are easy multiplication facts, especially the 5s and 10s facts, that help you solve harder facts.

You can use a fact you know, then add one group or subtract one group to get the answer you need.

The more you practice using 5s and 10s as anchors, the faster and more confident you will become with multiplication.

Put what you read to the test

You've worked through Benchmark Facts. Try answering a few questions to see what stuck — and what might deserve a quick reread before you move on.

Deriving Facts Using the Distributive Property

Deriving Facts Using the Distributive Property means breaking a multiplication problem into smaller, easier parts.

This helps when you do not know a fact right away, but you do know facts that are close to it.

For example, if you need to find \(6 \times 7\), you might break 7 into 5 and 2. Then you multiply 6 by each part and add the answers.

$$6 \times 7 = 6 \times (5 + 2) = (6 \times 5) + (6 \times 2) = 30 + 12 = 42$$

This is called the distributive property because the 6 is “shared” or “distributed” to both parts inside the parentheses.

Why this works

Imagine 7 groups of 6. If you split the 7 groups into 5 groups and 2 groups, you still have the same total number of items.

So multiplying by 7 is the same as multiplying by 5, multiplying by 2, and then putting the two amounts together.

$$6 \times 7 = 6 \times (5 + 2)$$

$$= (6 \times 5) + (6 \times 2)$$

You did not change the problem. You only broke it into easier pieces.

How to use the distributive property

  1. Choose a factor to break apart. Pick a number that can be split into facts you know well.
  2. Rewrite the problem. Use parentheses to show the split.
  3. Multiply each part. Find the partial products.
  4. Add the partial products. This gives the final answer.

Here is the pattern:

$$a \times (b + c) = (a \times b) + (a \times c)$$

You do not need to memorize the letters. Just remember: break apart, multiply each part, then add.

Picking helpful splits

Some splits are easier than others. Try to break a number into parts you already know.

  • Break 7 into 5 and 2
  • Break 8 into 5 and 3
  • Break 6 into 3 and 3
  • Break 9 into 5 and 4
  • Break 12 into 10 and 2

Using 5s, 10s, and doubles often makes multiplication easier.

Worked Example 1

Find \(4 \times 7\).

Break 7 into 5 and 2 because those facts are easy.

$$4 \times 7 = 4 \times (5 + 2)$$

Now multiply each part.

$$4 \times 5 = 20$$

$$4 \times 2 = 8$$

Add the partial products.

$$20 + 8 = 28$$

So, \(4 \times 7 = 28\).

Worked Example 2

Find \(8 \times 6\).

This time, break 6 into 3 and 3.

$$8 \times 6 = 8 \times (3 + 3)$$

Multiply each part.

$$8 \times 3 = 24$$

$$8 \times 3 = 24$$

Add them.

$$24 + 24 = 48$$

So, \(8 \times 6 = 48\).

You could also break 6 into 5 and 1.

$$8 \times 6 = 8 \times (5 + 1) = (8 \times 5) + (8 \times 1) = 40 + 8 = 48$$

Different splits can still give the same answer.

Worked Example 3

Find \(9 \times 7\).

Break 9 into 5 and 4.

$$9 \times 7 = (5 + 4) \times 7$$

You can multiply 7 by each part.

$$5 \times 7 = 35$$

$$4 \times 7 = 28$$

Add the partial products.

$$35 + 28 = 63$$

So, \(9 \times 7 = 63\).

This also matches the distributive property:

$$ (5 + 4) \times 7 = (5 \times 7) + (4 \times 7) $$

Worked Example 4

Find \(7 \times 12\).

Break 12 into 10 and 2.

$$7 \times 12 = 7 \times (10 + 2)$$

Multiply each part.

$$7 \times 10 = 70$$

$$7 \times 2 = 14$$

Add the partial products.

$$70 + 14 = 84$$

So, \(7 \times 12 = 84\).

This is a very helpful way to multiply when one factor is bigger.

Using an area model

An area model can help you see why the distributive property works.

Suppose you want to find \(3 \times 8\). Break 8 into 5 and 3.

You can think of one rectangle that is 3 rows by 8 columns. Then split it into two smaller rectangles: one that is 3 by 5 and one that is 3 by 3.

$$3 \times 8 = 3 \times (5 + 3)$$

$$= (3 \times 5) + (3 \times 3)$$

$$= 15 + 9 = 24$$

The two smaller rectangles together have the same area as the one big rectangle.

Important things to remember

  • You are not changing the problem. You are breaking one factor into parts.
  • Multiply each part. Do not forget any part.
  • Add the partial products. The final answer is the total.
  • Choose easy facts. Friendly numbers like 5, 10, 2, and doubles can help.

A common mistake

Sometimes students break apart a factor but only multiply one part.

For example, in \(6 \times (5 + 2)\), you must do both multiplications:

$$6 \times 5 = 30$$

$$6 \times 2 = 12$$

Then add:

$$30 + 12 = 42$$

If you forget one part, your answer will be too small.

Try thinking like this

  • \(7 \times 8\) can be thought of as \(7 \times 5 + 7 \times 3\)
  • \(6 \times 9\) can be thought of as \(6 \times 5 + 6 \times 4\)
  • \(4 \times 12\) can be thought of as \(4 \times 10 + 4 \times 2\)

This strategy helps you build fact fluency because it connects new facts to facts you already know.

Summary

The distributive property helps you solve multiplication problems by breaking one factor into smaller parts.

Then you multiply each part and add the partial products.

For example:

$$8 \times 7 = 8 \times (5 + 2) = (8 \times 5) + (8 \times 2) = 40 + 16 = 56$$

When a multiplication fact feels tricky, ask yourself: What number can I break apart into easier pieces?

Put what you read to the test

You've worked through Deriving Facts Using the Distributive Property. Try answering a few questions to see what stuck — and what might deserve a quick reread before you move on.

Commutative and Associative Properties of Multiplication

Commutative and Associative Properties of Multiplication

Multiplication can look tricky when there are several numbers to multiply. The good news is that multiplication has special properties that can make problems easier.

In this lesson, you will learn about two important properties:

  • Commutative Property of Multiplication
  • Associative Property of Multiplication

These properties help you rearrange factors so multiplication is faster and easier.

What are factors? Factors are the numbers being multiplied. In the problem \(3 \times 4\), the factors are 3 and 4.

1. Commutative Property of Multiplication

The commutative property means you can change the order of the factors, and the product stays the same.

Product means the answer to a multiplication problem.

Here is the rule:

$$a \times b = b \times a$$

That means:

  • \(2 \times 5 = 5 \times 2\)
  • \(4 \times 7 = 7 \times 4\)
  • \(9 \times 3 = 3 \times 9\)

Let’s check one:

\(2 \times 5 = 10\)

\(5 \times 2 = 10\)

The order changed, but the answer stayed the same.

This is helpful because sometimes one order is easier to think about than the other. For example, some students may know \(5 \times 8\) faster than \(8 \times 5\), even though both equal 40.

2. Associative Property of Multiplication

The associative property means that when multiplying three or more factors, you can change the way the factors are grouped, and the product stays the same.

Grouping is shown with parentheses.

Here is the rule:

$$(a \times b) \times c = a \times (b \times c)$$

That means:

  • \((2 \times 3) \times 4 = 2 \times (3 \times 4)\)
  • \((5 \times 2) \times 6 = 5 \times (2 \times 6)\)

Let’s check the first one:

\((2 \times 3) \times 4 = 6 \times 4 = 24\)

\(2 \times (3 \times 4) = 2 \times 12 = 24\)

The grouping changed, but the answer stayed the same.

This is useful because you can group numbers that are easy to multiply first.

Why these properties help

When you use these properties, you can choose an easier way to multiply.

  • The commutative property lets you switch the order.
  • The associative property lets you switch the grouping.

This can lower the amount you need to think about and help you solve problems faster.

Worked Example 1: Using the commutative property

Solve: \(6 \times 4\)

You may already know that \(4 \times 6 = 24\).

By the commutative property:

\(6 \times 4 = 4 \times 6 = 24\)

Answer: 24

Worked Example 2: Using the associative property

Solve: \((2 \times 5) \times 3\)

First way:

\((2 \times 5) \times 3 = 10 \times 3 = 30\)

Now regroup:

\(2 \times (5 \times 3) = 2 \times 15 = 30\)

Both ways give the same answer.

Answer: 30

Worked Example 3: Choosing an easier group

Solve: \(4 \times 25 \times 2\)

This problem has three factors. We can group the easiest pair first.

It is easy to multiply \(25 \times 2 = 50\).

So we regroup:

\(4 \times (25 \times 2) = 4 \times 50 = 200\)

You could also do:

\((4 \times 25) \times 2 = 100 \times 2 = 200\)

Both ways work, but grouping \(25\) and \(2\) may feel quicker for some students.

Answer: 200

Worked Example 4: Using both properties together

Solve: \(5 \times 3 \times 2\)

We can use the commutative property to change the order and the associative property to change the grouping.

First reorder the factors:

\(5 \times 3 \times 2 = 5 \times 2 \times 3\)

Now group the easy pair:

\((5 \times 2) \times 3 = 10 \times 3 = 30\)

Answer: 30

How to tell which property to use

  • If you are changing the order of two factors, use the commutative property.
  • If you are changing the grouping of three or more factors, use the associative property.
  • If a problem has three factors, you might use both properties to make it easier.

Important note

These properties work for multiplication. They help because the product stays the same when you change the order or grouping.

Try thinking like this:

  • Which factors are easy to multiply together?
  • Can I make a 10, 20, 50, or 100?
  • Would switching the order help me?

Quick Practice Ideas

  • \(7 \times 6 = 6 \times 7\)
  • \((3 \times 4) \times 5 = 3 \times (4 \times 5)\)
  • \(2 \times 9 \times 5\) can become \((2 \times 5) \times 9 = 10 \times 9 = 90\)

Summary

The commutative property of multiplication tells us that we can change the order of factors, and the product stays the same.

The associative property of multiplication tells us that we can change the grouping of factors, and the product stays the same.

These properties are useful because they help you choose easier multiplication facts, solve problems more quickly, and build fact fluency.

Put what you read to the test

You've worked through Commutative and Associative Properties of Multiplication. Try answering a few questions to see what stuck — and what might deserve a quick reread before you move on.

Fact Families and Inverse Relationships

Fact Families and Inverse Relationships

When we learn multiplication and division, it can feel like there are many facts to remember. The good news is that multiplication and division are connected. They are called inverse operations, which means they undo each other.

A fact family is a group of math facts that use the same three numbers. In multiplication and division, one fact family usually has 2 multiplication facts and 2 division facts.

For example, the numbers 3, 4, and 12 belong to the same fact family because they can make these four equations:

$$ 3 \times 4 = 12 $$ $$ 4 \times 3 = 12 $$ $$ 12 \div 3 = 4 $$ $$ 12 \div 4 = 3 $$

If you know one multiplication fact, you can use it to help with division facts too. That means you do not have to memorize as many facts one by one.

Main Idea 1: Multiplication joins equal groups

Multiplication tells us the total when we have equal groups.

  • \(3 \times 4 = 12\) means 3 groups of 4 make 12.

  • \(4 \times 3 = 12\) means 4 groups of 3 also make 12.

Even though the groups are described in a different order, the total is the same.

Main Idea 2: Division splits a total into equal groups

Division starts with the total and breaks it into equal groups or equal parts.

  • \(12 \div 3 = 4\) means 12 split into 3 equal groups gives 4 in each group.

  • \(12 \div 4 = 3\) means 12 split into 4 equal groups gives 3 in each group.

This is why division is the inverse of multiplication. Multiplication builds the total, and division takes the total apart.

Main Idea 3: The same three numbers stay together

In a multiplication and division fact family, the same three numbers are used again and again. If you know those three numbers, you can write the whole family.

For example, if the numbers are 5, 6, and 30, the fact family is:

$$ 5 \times 6 = 30 $$ $$ 6 \times 5 = 30 $$ $$ 30 \div 5 = 6 $$ $$ 30 \div 6 = 5 $$

Main Idea 4: How fact families help you

Fact families make math easier because one fact can help you find another fact.

  • If you know \(7 \times 8 = 56\), then you also know \(56 \div 8 = 7\).

  • If you know \(9 \times 4 = 36\), then you also know \(36 \div 9 = 4\).

This means multiplication facts and division facts work as a team.

How to Find a Fact Family

  1. Find the three numbers that belong together.

  2. Write the 2 multiplication facts.

  3. Write the 2 division facts.

Be careful: the biggest number in the family is usually the product, or total, in multiplication. That same number becomes the number you start with in division.

Worked Example 1

Write the fact family for 2, 9, and 18.

Step 1: Use the two smaller numbers to multiply.

$$ 2 \times 9 = 18 $$

Step 2: Turn the factors around.

$$ 9 \times 2 = 18 $$

Step 3: Use the total to make the division facts.

$$ 18 \div 2 = 9 $$ $$ 18 \div 9 = 2 $$

So the fact family is 2, 9, and 18.

Worked Example 2

If you know \(6 \times 7 = 42\), what two division facts can you find?

The total is 42. Use 42 and divide by each factor.

$$ 42 \div 6 = 7 $$ $$ 42 \div 7 = 6 $$

So one multiplication fact gives us two division facts.

Worked Example 3

A teacher puts 24 pencils into 4 equal cups. How many pencils are in each cup?

This is a division problem because we know the total and the number of groups.

$$ 24 \div 4 = 6 $$

There are 6 pencils in each cup.

Now use the inverse relationship to check the answer:

$$ 6 \times 4 = 24 $$

The answer makes sense because multiplying brings us back to the total.

Worked Example 4

Find the missing number: \(35 \div 5 = \square\)

Think: what multiplication fact makes 35 using 5?

$$ 5 \times 7 = 35 $$

So:

$$ 35 \div 5 = 7 $$

Using multiplication can help you solve division quickly.

Tips to Remember

  • Multiplication and division are inverse operations.

  • A fact family uses the same 3 numbers.

  • Most multiplication/division fact families have 4 facts.

  • If you know a multiplication fact, you can use it to solve related division facts.

  • Division can be checked with multiplication.

Watch Out For These Mistakes

  • Do not bring in a new number. A fact family only uses the same three numbers.

  • Do not divide the smaller number by the larger number in these basic fact families. Usually, the largest number is the total.

  • Check that your multiplication and division facts match each other.

Quick Practice to Think About

  • What is the fact family for 4, 8, and 32?

  • If \(8 \times 5 = 40\), what is \(40 \div 8\)?

  • If \(27 \div 3 = 9\), what multiplication fact checks it?

Summary

Fact families show how multiplication and division are connected. They use the same three numbers to make related equations.

Because multiplication and division are inverse operations, one can help you solve the other. When you learn one fact, you can use it to find more facts, making math faster and easier.

Put what you read to the test

You've worked through Fact Families and Inverse Relationships. Try answering a few questions to see what stuck — and what might deserve a quick reread before you move on.

Tape Diagrams for Multiplicative Comparison

Lesson: Tape Diagrams for Multiplicative Comparison

Sometimes a word problem says one amount is 2 times as many, 3 times as many, or 4 times as many as another amount. This is called a multiplicative comparison.

A tape diagram is a simple drawing made of rectangles, or boxes, placed in a row. Tape diagrams help us see the comparison and understand what math to do.

In this lesson, you will learn how to use tape diagrams to solve problems about times as many.

What does “times as many” mean?

When a problem says, “Lena has 3 times as many stickers as Max,” it means Lena has 3 equal groups of Max’s amount.

This is different from saying “3 more.”

  • 3 more means add 3.
  • 3 times as many means multiply by 3.

So if Max has 4 stickers, and Lena has 3 times as many, then Lena has:

$$3 \times 4 = 12$$

How a tape diagram works

A tape diagram uses equal-sized boxes to show equal amounts.

If one box stands for 4, then 3 boxes stand for 3 groups of 4.

For example:

Max: [ 4 ]

Lena: [ 4 ][ 4 ][ 4 ]

The tape diagram shows that Lena has 3 boxes because she has 3 times Max’s amount.

Steps for solving multiplicative comparison problems

  1. Read the problem carefully. Look for the words times as many.
  2. Find the smaller amount or the one-box amount.
  3. Draw a tape diagram. Use 1 box for the smaller amount.
  4. Draw more equal boxes for the larger amount.
  5. Multiply or divide to find the unknown.
  6. Check your answer with the story.

Worked Example 1: Find the larger amount

Sam has 5 toy cars. Mia has 3 times as many toy cars as Sam. How many toy cars does Mia have?

Step 1: Find the smaller amount.

Sam has 5. That is the amount in 1 box.

Sam: [ 5 ]

Mia: [ 5 ][ 5 ][ 5 ]

Step 2: Count the equal groups.

Mia has 3 boxes, and each box is 5.

$$3 \times 5 = 15$$

Answer: Mia has 15 toy cars.

Worked Example 2: Another larger amount problem

A tree is 4 times as tall as a plant. The plant is 2 feet tall. How tall is the tree?

Step 1: Draw the plant.

Plant: [ 2 ]

Step 2: Draw the tree as 4 equal boxes.

Tree: [ 2 ][ 2 ][ 2 ][ 2 ]

Step 3: Multiply.

$$4 \times 2 = 8$$

Answer: The tree is 8 feet tall.

Worked Example 3: Find the smaller amount

Noah has 18 marbles. He has 3 times as many marbles as Eli. How many marbles does Eli have?

This time, the larger amount is given. We need to find the smaller amount.

Step 1: Draw the tape diagram.

Noah has 3 equal boxes that together make 18.

Noah: [ ? ][ ? ][ ? ] = 18

Eli: [ ? ]

Since the 3 boxes are equal, split 18 into 3 equal parts.

$$18 \div 3 = 6$$

So each box is 6.

Eli: [ 6 ]

Noah: [ 6 ][ 6 ][ 6 ]

Answer: Eli has 6 marbles.

Worked Example 4: Find an unknown comparison amount

Sara read 6 books. Ben read 4 times as many books as Sara. How many books did Ben read?

Step 1: One box is Sara’s amount.

Sara: [ 6 ]

Ben: [ 6 ][ 6 ][ 6 ][ 6 ]

Step 2: Multiply.

$$4 \times 6 = 24$$

Answer: Ben read 24 books.

How to know whether to multiply or divide

  • If you know 1 box and need the total of many equal boxes, multiply.
  • If you know the total and need to find the value of 1 box, divide.

For example:

  • 1 box is 7, and there are 3 boxes: $$3 \times 7 = 21$$
  • 3 boxes total 21, so 1 box is: $$21 \div 3 = 7$$

Important words to watch for

These words often mean multiplicative comparison:

  • times as many
  • times as much
  • twice as many means 2 times as many
  • 3 times as long
  • 4 times as tall

Be careful!

Do not mix up times as many with more than.

Example:

  • “8 is 2 more than 6” means $$6 + 2 = 8$$
  • “12 is 2 times as many as 6” means $$2 \times 6 = 12$$

Try thinking with boxes

If Ruby has 7 pencils and Jack has 2 times as many, think:

Ruby: [ 7 ]

Jack: [ 7 ][ 7 ]

Then solve:

$$2 \times 7 = 14$$

So Jack has 14 pencils.

Another way tape diagrams help

Tape diagrams help you organize the information before doing the math. They make it easier to see:

  • who has the smaller amount,
  • who has the larger amount,
  • how many equal groups there are,
  • and whether to multiply or divide.

Quick practice thinking

If one box is 3 and there are 5 boxes, the total is:

$$5 \times 3 = 15$$

If 5 equal boxes together make 15, then one box is:

$$15 \div 5 = 3$$

Summary

A tape diagram is a row of equal boxes that helps show a multiplicative comparison. When a problem says times as many, draw 1 box for the smaller amount and several equal boxes for the larger amount.

If you know the amount in 1 box, multiply to find the total. If you know the total for several equal boxes, divide to find the amount in 1 box.

Using tape diagrams can help you understand the story, choose the right operation, and solve word problems with confidence.

Put what you read to the test

You've worked through Tape Diagrams for Multiplicative Comparison. Try answering a few questions to see what stuck — and what might deserve a quick reread before you move on.

Finding Unknown Factors

Finding Unknown Factors means figuring out the missing number in a multiplication equation.

For example, in the equation \(3 \times \square = 12\), the box is the unknown factor. We need to find what number times 3 equals 12.

This is an important skill because it helps you use what you already know about multiplication facts. It also helps you get ready for harder math later.

What is a factor?

A factor is a number that is multiplied by another number. In \(4 \times 5 = 20\), the numbers 4 and 5 are factors.

If one factor is missing, we can find it by asking: What number times this factor gives the product?

How to find an unknown factor

  1. Look at the multiplication equation.

  2. Find the number you know and the total, called the product.

  3. Ask yourself what number times the known factor equals the product.

  4. Use multiplication facts you know, or use division to help.

For example, in \(6 \times \square = 24\), we ask, “What number times 6 equals 24?” Since \(6 \times 4 = 24\), the unknown factor is 4.

Multiplication and division work together

Finding an unknown factor is closely connected to division. If you know \(7 \times \square = 35\), you can think of it as \(35 \div 7 = \square\).

So if you forget a multiplication fact, division can help you find the missing number.

Use equal groups to think about it

Multiplication can mean equal groups. In \(5 \times \square = 20\), you have 5 equal groups that make 20 altogether.

To find how many are in each group, you can share 20 into 5 equal groups:

$$20 \div 5 = 4$$

So \(5 \times 4 = 20\).

Use arrays to think about it

An array is a picture with rows and columns. If you know an array has 18 squares and 3 rows, you can find how many squares are in each row.

That means solving:

$$3 \times \square = 18$$

Since \(18 \div 3 = 6\), the unknown factor is 6.

Worked Example 1

Find the unknown factor in \(2 \times \square = 14\).

Step 1: Ask, “What number times 2 equals 14?”

Step 2: Think of your multiplication facts.

$$2 \times 7 = 14$$

So the unknown factor is 7.

Worked Example 2

Find the unknown factor in \(\square \times 8 = 40\).

Step 1: Ask, “What number times 8 equals 40?”

Step 2: Use division if needed.

$$40 \div 8 = 5$$

So:

$$5 \times 8 = 40$$

The unknown factor is 5.

Worked Example 3

A teacher puts 24 markers into 6 equal cups. How many markers are in each cup?

This can be written as:

$$6 \times \square = 24$$

Now divide:

$$24 \div 6 = 4$$

So there are 4 markers in each cup.

Worked Example 4

A rectangle has an area of 36 square units. One side length is 9 units. What is the other side length?

This means:

$$9 \times \square = 36$$

Ask, “What number times 9 equals 36?”

$$36 \div 9 = 4$$

So the other side length is 4 units.

Tips for success

  • Use multiplication facts you already know.

  • If you get stuck, turn the multiplication equation into a division equation.

  • Check your answer by multiplying the factors.

  • Look for equal groups, rows, columns, or area models to help you picture the problem.

Let’s check by multiplying

If you think the answer to \(4 \times \square = 28\) is 7, check it:

$$4 \times 7 = 28$$

The equation is true, so 7 is correct.

Common mistake to avoid

Sometimes students mix up the product and the factor. In \(3 \times \square = 15\), the missing number is not 12 or 18. You must find the number that makes the equation true.

Since:

$$3 \times 5 = 15$$

the unknown factor is 5.

Practice thinking

Here are some questions to try on your own:

  • \(7 \times \square = 49\)

  • \(\square \times 6 = 30\)

  • \(8 \times \square = 56\)

  • \(\square \times 9 = 63\)

To solve each one, ask: What number times the known factor equals the product?

Summary

Finding an unknown factor means finding the missing number in a multiplication equation.

You can solve it by using multiplication facts or by using division. Equal groups, arrays, and area models can also help you understand what the missing factor means.

Always check your answer by multiplying to see if the equation is true.

Put what you read to the test

You've worked through Finding Unknown Factors. Try answering a few questions to see what stuck — and what might deserve a quick reread before you move on.

Identifying Patterns in the Multiplication Table

Identifying Patterns in the Multiplication Table

A multiplication table is more than a chart of answers. It is full of patterns that can help you understand multiplication facts and remember them more easily.

When you study the table carefully, you can notice how numbers grow across rows, down columns, and even along diagonals. These patterns show how multiplication works with equal groups and repeated addition.

In this lesson, you will learn how to find patterns in the multiplication table and use them to solve facts faster and more confidently.

What is a multiplication table?

A multiplication table shows the products of two numbers. A product is the answer to a multiplication problem.

For example, in the fact \(4 \times 3 = 12\), the numbers 4 and 3 are factors, and 12 is the product.

If you look at a multiplication table, each row and each column follows a pattern. These patterns can help you predict the next number without having to start over each time.

Pattern 1: Horizontal patterns across a row

When you move across a row, you keep multiplying by the same number. This means the products grow by equal jumps.

For example, in the 4s row:

$$ 4,\ 8,\ 12,\ 16,\ 20,\ 24 $$

Each number increases by 4.

This happens because:

$$ 4 \times 1 = 4 $$ $$ 4 \times 2 = 8 $$ $$ 4 \times 3 = 12 $$

Each time the second factor goes up by 1, one more group of 4 is added.

You can think of it like repeated addition:

$$ 4,\ 4+4=8,\ 8+4=12,\ 12+4=16 $$

So every row has a skip-counting pattern.

  • The 2s row increases by 2.
  • The 5s row increases by 5.
  • The 10s row increases by 10.

Pattern 2: Vertical patterns down a column

Columns also follow patterns. When you move down a column, the products increase by the same amount each time.

For example, in the 6s column:

$$ 6,\ 12,\ 18,\ 24,\ 30 $$

Each number increases by 6.

That is because:

$$ 1 \times 6 = 6 $$ $$ 2 \times 6 = 12 $$ $$ 3 \times 6 = 18 $$

Each step down adds one more group of 6.

This means rows and columns both show skip-counting. The table is full of repeated addition patterns.

Pattern 3: The table is the same across the middle

A very important pattern in the multiplication table is that facts can switch places and still have the same answer.

For example:

$$ 3 \times 4 = 12 $$ $$ 4 \times 3 = 12 $$

This means the table has a matching pattern across the diagonal from top left to bottom right.

You may notice that the answer in row 3, column 4 is the same as the answer in row 4, column 3.

This happens because changing the order of the factors does not change the product.

More examples:

  • \(2 \times 7 = 14\) and \(7 \times 2 = 14\)
  • \(5 \times 8 = 40\) and \(8 \times 5 = 40\)
  • \(6 \times 9 = 54\) and \(9 \times 6 = 54\)

This pattern helps you learn fewer facts. If you know \(3 \times 8\), then you also know \(8 \times 3\).

Pattern 4: Diagonal patterns

There are interesting patterns along diagonals in the multiplication table.

One important diagonal is the one with square numbers:

$$ 1 \times 1 = 1 $$ $$ 2 \times 2 = 4 $$ $$ 3 \times 3 = 9 $$ $$ 4 \times 4 = 16 $$ $$ 5 \times 5 = 25 $$

These are called square facts because both factors are the same.

The diagonal of square facts is useful because these facts often stand out and are easy to remember.

Other diagonals can also show patterns. For example, if you look at:

$$ 2 \times 3 = 6 $$ $$ 3 \times 4 = 12 $$ $$ 4 \times 5 = 20 $$ $$ 5 \times 6 = 30 $$

The products are growing, and the jumps get bigger. This shows that multiplication patterns can change in interesting ways along diagonals.

Pattern 5: Recursive patterns

A recursive pattern means you can find the next number by using the number before it.

In multiplication rows and columns, you can often find the next product by adding the same factor again.

For example, in the 7s row:

$$ 7,\ 14,\ 21,\ 28,\ 35 $$

To get each new product, add 7 to the one before it.

  • \(7 + 7 = 14\)
  • \(14 + 7 = 21\)
  • \(21 + 7 = 28\)
  • \(28 + 7 = 35\)

This helps when you do not remember a fact right away. If you know \(7 \times 4 = 28\), then you can find \(7 \times 5\) by adding one more 7:

$$ 28 + 7 = 35 $$

Helpful number patterns in special rows

Some rows have patterns that are easy to spot.

The 2s row

  • It is just double the other number.
  • Example: \(2 \times 8 = 16\)

The 5s row

  • The products end in 0 or 5.
  • Example: \(5, 10, 15, 20, 25, 30\)

The 10s row

  • The products end in 0.
  • Example: \(10 \times 6 = 60\)

The 9s row

  • The products increase by 9 each time.
  • The digits often have a pattern: \(09, 18, 27, 36, 45, 54, 63, 72, 81, 90\)

These patterns make fact fluency easier because your brain can notice regular number changes.

Worked Example 1: Finding a horizontal pattern

Look at the 3s row:

$$ 3,\ 6,\ 9,\ 12,\ 15 $$

Question: What comes next?

Step 1: Notice the pattern. Each number increases by 3.

Step 2: Add 3 to the last number.

$$ 15 + 3 = 18 $$

Answer: The next number is 18, so \(3 \times 6 = 18\).

Worked Example 2: Using a recursive pattern

Question: If you know \(6 \times 4 = 24\), how can you find \(6 \times 5\)?

Step 1: Moving from \(6 \times 4\) to \(6 \times 5\) means adding one more group of 6.

Step 2: Add 6 to 24.

$$ 24 + 6 = 30 $$

Answer: \(6 \times 5 = 30\).

Worked Example 3: Using the matching pattern across the table

Question: If you know \(8 \times 4 = 32\), what is \(4 \times 8\)?

Step 1: Notice that the factors are the same numbers in a different order.

Step 2: Use the table pattern that switched factors give the same product.

$$ 8 \times 4 = 32 $$ $$ 4 \times 8 = 32 $$

Answer: \(4 \times 8 = 32\).

Worked Example 4: Finding a diagonal square fact

Question: What is \(7 \times 7\)?

Step 1: This is a square fact because both factors are 7.

Step 2: Find it on the diagonal of square facts, or use what you know about the 7s pattern.

$$ 7 \times 7 = 49 $$

Answer: The product is 49.

How patterns help you solve multiplication facts

  • They help you predict the next product.
  • They help you check if an answer makes sense.
  • They help you remember facts by noticing number rules.
  • They help you use facts you already know to find new ones.

For example, if someone says \(5 \times 6 = 35\), you can check the 5s pattern. The 5s row goes:

$$ 5,\ 10,\ 15,\ 20,\ 25,\ 30 $$

So \(5 \times 6 = 30\), not 35.

Tips for studying multiplication table patterns

  1. Pick one row and say the products out loud as skip-counting.
  2. Look for how much the numbers increase each time.
  3. Find matching facts like \(3 \times 7\) and \(7 \times 3\).
  4. Practice square facts like \(4 \times 4\), \(6 \times 6\), and \(8 \times 8\).
  5. Use one known fact to find the next fact by adding the same number again.

Summary

The multiplication table is full of useful patterns. Across rows and down columns, products grow by equal amounts. Across the middle, matching facts such as \(3 \times 4\) and \(4 \times 3\) have the same answer.

Diagonals can show special patterns, especially square facts like \(5 \times 5 = 25\). Recursive patterns help you find the next product by adding the same factor again. When you notice these patterns, multiplication becomes easier to understand and remember.

Put what you read to the test

You've worked through Identifying Patterns in the Multiplication Table. Try answering a few questions to see what stuck — and what might deserve a quick reread before you move on.