Adding negative numbers

Home learning focus

In this lesson you will learn how to add negative numbers.

This lesson includes:

  • a learning summary
  • two activities

Learn

Adding positive and negative numbers

A number line will help you add and subtract numbers.

When adding positive numbers, count to the right.

When adding negative numbers, count to the left.

Example 1

Let's look at an example.

Calculate -5 + 4

First, find the starting number: -5

Then, count 4 places to the right.

The answer is -1.

Calculations with two signs next to each other

Sometimes a calculation will have two signs, either + or , next to each other.

For example:

  • 6 + –3
  • 4 – –3
  • 6 – +3

If the signs are different, you always subtract.

If the signs are the same, you always add the numbers together.

  • 6 + –3 = 6 – 3 = 3
  • 4 – –3 = 4 + 3 = 7
  • 6 – +3 = 6 – 3 = 3

Adding negative numbers

When you add negative numbers in a calculation, the signs will always be different (ie + and ). You must therefore always subtract the second number.

Examples:

5 +-15 = 5 - 15 = -10

-5 + -15 = -5 - 15 = -20

Practise

Activity 1

Negative numbers in context

Have a go at these interactive questions from MyMaths, Oxford University Press.

You will practise subtracting positive and negative numbers in real-world scenarios.

To navigate the activities, click on the numbered buttons at the sides of the screen. Click 'next' to move onto the next page within each section.

Negative numbers in context

Activity 2

Odd one out

Have a go at this worksheet from Teachit. You can print it out or write your answers on a piece of paper.

There are four tables. In each table, the rows and columns should add up to the same value. The value is different for each table.

Can you work out which cell in each table is the odd one out?

Odd one out

There's more to learn

Have a look at these other resources around the BBC and the web.

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BBC Bitesize Daily
Simon Singh's Numbers
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