Topics
3. Multiplication and division
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Australia
Year 5

3.11 Factors

Lesson
Practice

Are you ready?

Being able to recall our  multiplication facts  will help us in this lesson. Let's try a practice problem now.

Examples

Example 1

What is 4 \times 8?

Worked Solution
Create a strategy

We can think of it as 4 groups of 8 like in the array below which has 4 rows of 8 squares.

An array of squares with 4 rows and 8 columns
Apply the idea

There is a total of 32 squares in the array. So:

4\times8=32

Idea summary

There are different ways to solve multiplication, including repeated addition and using arrays. We can also multiply our numbers in a different order, so 3\times4 has the same answer as 4\times3.

Factor pairs

This video will show us how to find all the factors for a number.

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Examples

Example 2

If we multiply 4 by 14, we get 56, so 4 and 14 make a factor pair of 56.

Which of the following options is also a factor pair of 56?

A
14 and 2
B
4 and 7
C
8 and 7
D
2 and 2
Worked Solution
Create a strategy

Multiply each pair of numbers together.

Apply the idea

Option A: \begin{array}{c} &&1&4 \\ &\times &&2\\ \hline &&2&8 \\ \hline \end{array}

Option B: 4\times7=28

Option C: 8\times7=56

Option D: 2\times2=4

Only the pair in option C multiplies to 56. The answer is option C.

Idea summary

All numbers have at least one factor pair, 1 and itself.

To check if a pair of numbers is a factor pair of a given number, multiply the pair of numbers together.

Outcomes

AC9M5N02

express natural numbers as products of their factors, recognise multiples and determine if one number is divisible by another

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