Add and Subtract Positive and Negative Numbers Mentally

The calculations in this activity should be done in your head before writing down the answers.

 

It might seem tough, but it's really good practice for solving problems quickly!

 

It is really important to learn the rule for negative numbers, so let's recap it here.

 

When two signs are written next to each other:

If the two signs are different, they make a negative sign.

If the two signs are the same, they make a positive sign.

 

This means that:

+ and - make a negative

- and + make a negative

+ and + make a positive

- and - make a positive

 

For example, when adding a negative number, you have + and - together, so the answer will be negative:

7 + -9 = 7 - 9 = -2

 

When subtracting a negative number, you have - and - together, so the answer will be positive:

3 - -5 = 3 + 5 = 8

 

So, let's have a look at some tough ones!

 

Examples

(-9) - (-8) = (-9) + 8 = 8 - 9 = -1

82 + (-6) = 82 - 6 = 76

(-5) - 5 = -10

 

 

Has your brain given up? Don't panic, we'll go through them together.

 

Let's get started!!