6.07 Multiplication by 4

Lesson

Ideas

Multiplication looks at equally sized groups. Doubling means multiplying equally sized  groups by  2. Can you solve this problem?

Examples

Example 1

Find 9\times2.

Worked Solution
Create a strategy

Remember 9 \times 2 is the same as 2 \times 9. This can be thought of as 2 groups of 9 stars.

Apply the idea

In the above image there are 18 stars altogether.

Idea summary

Multiplying by two is the same as doubling and can be thought of as the total of two equally sized groups.

Multiply numbers by 4

4 groups is twice (two times) as many as 2 groups. Let's look at how to multiply numbers by 4.

Examples

Example 2

Find the product of 4\times 4.

Worked Solution
Create a strategy

This can be thought of as 4 groups of 4 squares as shown below.

Apply the idea

In the above image there are 16 squares in total.4 \times 4 = 16

Reflect and check

We could also use the Double, Double strategy:

Idea summary

To solve questions with 4 times tables, you can use the Double, Double strategy. That means you double the number, then double the answer.

Outcomes

MA2-6NA

uses mental and informal written strategies for multiplication and division