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Math · Grade 3 Math

Chapter 1: Multiplication and Division as Equal Groups

Equal Groups and Multiplication

A short way to write repeated addition.

Lesson
1
Time
About 12 minutes
0 of 9 done
Part 1 of 7Let's Learn

Step 1: Let's Learn

Read it, or press Listen and follow the words.

Watch the idea first — 52 seconds. Then read on, and try it yourself in the next step.

Last year you added equal groups: 4 + 4 + 4 = 12. There is a shorter way to write it.

Three groups of four is written 3 × 4.

Multiplication is a short way of adding equal groups. The symbol is ×.

How to read it

In 3 × 4, the 3 is how many groups and the 4 is how many in each group.

The answer has a name.

Product is the answer to a multiplication.

Step 2: Try It Yourself

Change the rows and read both sentences underneath.

Each row is a group. Compare the two sentences underneath.

4 + 4 + 4 = 12

3 × 4 = 12

3 rows of 4 makes 12.

The same total, laid out every way it goes. What will not fit sits outside.

3 × 4 = 12. 3 and 4 are a factor pair of 12.

Pairs you have found

  • 3 × 4

Step 3: In Real Life

In the kitchen

An egg box holds 2 rows of 6 eggs. A cook does not count every egg. They see 2 groups of 6 and know it is 2 × 6 = 12. Every full box is a multiplication waiting to be read.

Step 4: Watch an Example

One step at a time.

Watch Ana Write a Product

Ana sees 5 plates with 3 buns on each.

  1. Step 1

    She counts the groups: 5 plates.

Step 5: Your Turn

Practice makes it stick.

The Bike Rack

Problem 1 of 2

6 bicycles are parked. Each has 2 wheels. Write this as a multiplication and solve it.

wheels

The Egg Boxes

Problem 2 of 2

4 boxes each hold 6 eggs. How many eggs are there?

eggs

Write It the Short Way

1 of 4

3 groups of 5. What is the product?

2 of 4

2 groups of 8. What is the product?

3 of 4

In 7 × 4, how many groups are there?

4 of 4

In 7 × 4, how many are in each group?

Build the Array

Build it, then check.

Build 3 rows of 4.

Set the rows and the columns.

1 = 1

1 row of 1 makes 1.

Step 6: Quick Check

Show what you know.

Question 1 of 2

4 groups of 5. What is the product?

Question 2 of 2

What does multiplication do?

What You Learned

  • Multiplication is a short way to add equal groups.
  • 3 × 4 means 3 groups of 4.
  • The answer is called the product.
For the grown-up

Multiplication is equal groups before it is a fact to recall. Three fours is three groups of four, and division is the same picture asked from the other end.

Watch for multiplication and division being learned as separate subjects. They are one relationship, and a child who sees that halves what there is to remember.

When they are stuck on a division, ask the multiplication instead: "what times 4 gives 24?" Nearly every child can answer that when they cannot answer 24 divided by 4.

Multiplication is shorthand, not a new ideaFour groups of 5 can be written 5 + 5 + 5 + 5, or written 4 × 5. Both mean the same thing and both give 20. Multiplication was invented because writing out long strings of the same number is slow and easy to get wrong. Nothing about it is mysterious — it is addition, packaged.

Reading the two numbers correctlyIn 4 × 5, the 4 is the number of groups and the 5 is how many are in each group. Read it as "four groups of five". The two numbers play different roles even though they sit side by side, and telling them apart is what lets you match an equation to a picture or a story.

The groups must be equalMultiplication only applies when every group holds the same number. Three plates with 4, 4 and 4 biscuits is 3 × 4. Three plates with 4, 5 and 3 is not multiplication at all — you have to add. Checking that the groups really are equal is the first thing to do before reaching for a times table.

Write it the long way firstThree plates. Four buns on each. The long way: 4 + 4 + 4 = 12 The short way: 3 × 4 = 12 The 3 is how many groups. The 4 is how many in each. Nothing new happened. It is the same adding, written shorter.