Check Answers to Calculations Using the Inverse Operation

Did you know that we can check answers to addition questions using subtraction, and check subtraction answers using addition?

 

This is called using the inverse operation. 

 

In this activity, we are going to practise checking our answers using the inverse operation.

 

 

Example

Look at this addition question.

7,245 + 355 = 

 

We can work out the answer mentally or use a written method.

7,245 + 355 = 7,600

 

It is always worth checking our answers even when we think we have got the answer correct. 

We can all make mistakes from time to time!

 

Let's check

The inverse of addition is subtraction.

So we work out:

7,600 - 355 = 7,245

 

or we could do

7,600 - 7,245 = 355

 

We must actually do the calculation to check the answer!

 

 

Let's have a look at another example using subtraction.

1,530 - 820 = 710

 

Now, let's use the inverse operation to check we have the correct answer.

820 + 710 = 1,530

 

 

Now it's your turn to have a go at using the inverse operation to check some answers - good luck!