Topics
6. Multiplication strategies
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AustraliaNSW
Stage 2

6.07 Multiplication by 2

Lesson
Practice
Lesson

Introduction

Introduction to the lesson

Are you ready?

Can you write  repeated addition  as a multiplication number sentence? Try this question.

Examples

Example 1

Write this addition as a multiplication.

2+2+2

Worked Solution
Create a strategy

To write this as a multiplication use: Number of groups \times amount in each group.

Apply the idea

There are 3 groups of 2.

\displaystyle 2+2+2\displaystyle =\displaystyle 3 \times 2
Idea summary

If we are adding groups of the same size, we can also write it as a multiplication:

\text{Number of groups} \times \text{Amount in each group}

Multiply numbers by 2

Let's look at how to double or multiply numbers by 2.

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Examples

Example 2

Find the product of 2\times 8.

Worked Solution
Create a strategy

This can be thought of as 2 groups of 8 stars, as represented in the picture below.

The image shows 2 circles with 8 stars each inside.
Apply the idea

In the above image there are 16 stars in total.2 \times 8 = 16

Idea summary

Multiplying by two is the same as doubling. We always multiply equally sized groups.

Outcomes

MA2-6NA

uses mental and informal written strategies for multiplication and division

MA2-8NA

generalises properties of odd and even numbers, generates number patterns, and completes simple number sentences by calculating missing values

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