# Mathematics

L.C: Using inverse calculations to check answers. Using inverse calculations

What is an inverse calculation?

An inverse calculation uses the opposite operation to check whether the answer is correct.

For example: If we add 81 + 29  is the total 100 or 110?

We can check the answer by subtraction

81             81

+29   or  +  29

100            110

Let's  check

Work out these subtractions to check which answer was correct. We should end up with 81 if the answer is correct.

100       110

- 29      - 29

______    _____

Remember to show when renaming That's right 81 + 29 = 110

When checking using the inverse

110 - 29 = 81

Can you see that we have the same numbers in both addition and subtraction?

This is how we know the answer is correct. Once you have worked out the answers complete the inverse calculations below to check.

1.  ????      2.  ????     3. ????       4.             Complete

+ 5004      + 3153    + 2044        +            this inverse

8017         6276       8068                      independently Once you have worked out the answers complete the inverse calculations to check. (Write the inverse calculation underneath the subtraction like above.)

Challenge 