Topics
4. Subtraction
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AustraliaVIC
Level 3

4.01 Subtraction and number lines

Lesson
Practice
Lesson

Are you ready?

Knowing how to  count back  can help us with subtracting on a number line.

Examples

Example 1

Create a pattern by subtracting 1 each time.

6,\,⬚,\,⬚,\,⬚

Worked Solution
Create a strategy

We can use a number line to find how much the numbers are decreasing by each time.

Apply the idea

Plot 6 on a number line and jump back by 1 to get to 5:

12345678

Now we complete the pattern by subtracting 1 each time:

\displaystyle 5-1\displaystyle =\displaystyle 4Subtract 1
\displaystyle 4-1\displaystyle =\displaystyle 3Subtract 1

So the complete pattern is: 6,\, 5,\, 4,\, 3.

Subtraction and number lines

We are going to use a number line to see how to find the difference between two numbers.

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Examples

Example 2

Use the number line to help you find the value of 35 - 24.

10152025303540
Worked Solution
Create a strategy

Plot the first number on a number line then jump back the amount of the second number.

Apply the idea

Plot 35 on the number line and jump back by 24 to get 11:

10152025303540

35 -24 = 11

Idea summary

When adding to a number, jump forward (to the right).

A number line with 4 curved arrows showing jumps to the right.

When subtracting from a number, jump backwards (to the left).

A number line with 4 curved arrows showing jumps to the left.

Outcomes

VCMNA133

Recall addition facts for single-digit numbers and related subtraction facts to develop increasingly efficient mental strategies for computation

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