Topics
3. Multiplication strategies
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Australia
Year 4

3.01 Repeated addition as multiplication

Lesson
Practice
Lesson

Are you ready?

Can you write a repeated addition as a multiplication number sentence?

Examples

Example 1

Write this addition as a multiplication. 3+3+3+3+3+3

Worked Solution
Create a strategy

We can rewrite the addition as a multiplication using: \text{Number of groups}\times\text{Amount in each group}

Apply the idea

We have 6 groups of 3. We can rewrite this as multiplication: 3+3+3+3+3+3=6\times 3

Idea summary

We can rewrite the addition as a multiplication using: \text{Number of groups}\times\text{Amount in each group}

Repeated addition

Let's use what we know about writing repeated addition as multiplication number sentences and use it to solve questions as well.

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Examples

Example 2

Answer the following:

a

Write this addition as a multiplication:\,\, 4+4+4+4+4

Worked Solution
Create a strategy

We can rewrite the addition as a multiplication using: \text{Number of groups}\times\text{Amount in each group}

Apply the idea

We have 5 groups of 4. We can rewrite this as multiplication: 4+4+4+4+4=5\times 4

b

Find the value of 5 \times 4.

Worked Solution
Create a strategy

Use skip counting or a multiplication table.

Apply the idea

By skip counting by 4 five times, we have4, \,8, \,12, \,16, \,20

So, 5 \times 4=20.

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}

To find the answer we can use skip counting or a multiplication table.

Outcomes

AC9M4N09

follow and create algorithms involving a sequence of steps and decisions that use addition or multiplication to generate sets of numbers; identify and describe any emerging patterns

AC9M4A02

recall and demonstrate proficiency with multiplication facts up to 10 x 10 and related division facts; extend and apply facts to develop efficient mental strategies for computation with larger numbers without a calculator

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