# 4.01 Subtraction and number lines

Lesson

## Ideas

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:

Now we complete the pattern by subtracting 1 each time:

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.

### Examples

#### Example 2

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

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:

35 -24 = 11

Idea summary

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

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

### Outcomes

#### MA2-5NA

uses mental and written strategies for addition and subtraction involving two-, three-, four and five-digit numbers