Using inverse operations to check calculations

Introduced in the Year 4 curriculum as: "Estimate and use inverse operations to check answers to an addition or subtraction calculation"

When you do a difficult calculation, it is often a good idea to check your

answer.

One way to do this is to re-do the calculation in reverse.

This is called doing the inverse.

+ is the opposite to -

and

x is the opposite to ÷

Example 1:

If you think 52 ÷ 4 = 13

You could check by doing 13 x 4 to see if you get back to 52.

Example 2:

If you think 63 - 24 = 39

You could check by doing 39 + 24 to see if you get back to 63.


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