*This Math quiz is called 'Checking Calculations with Inverse Operations' and it has been written by teachers to help you if you are studying the subject at elementary school. Playing educational quizzes is a fun way to learn if you are in the 1st or 2nd grade - aged 6 to 8.*

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In order to check a calculation, it is useful to know the inverse (or opposite) operation. For example, the inverse operation of addition is subtraction so to check 5 + 6 = 11, you could try 11 - 6 = 5 or 11 - 5 = 6. Another way of checking an addition calculation would be to add the numbers up in a different order - this of course does not work for subtraction!

Can you check the calculations by adding in a different order or by using the inverse operation?

1.

How do you know that 20 - 10 = 10?

Because I know 10 + 10 = 20

Because it's a subtraction

Because it's an addition

Because I know about subtraction

Using an addition fact can help to solve a subtraction

2.

How could you check 62 + 38 = 100?

By taking away 100

By finding the difference between 62 and 38

By subtracting 100 from 62

By subtracting 38 from 100

If 62 + 38 = 100 is correct, then 100 - 38 should give an answer of 62

3.

Which calculation could you use to check that 16 - 9 = 7 is correct?

16 + 9 = 7

9 + 7 = 16

7 - 16 = 9

7 - 9 = 16

If 9 subtracted from 16 leaves 7, then by adding the 9 back again, you should be back to where you started

4.

What does 'inverse operation' mean?

Doing the calculation upside down

Making a mistake on purpose

The opposite operation

A medical procedure

The inverse of subtraction is addition, the inverse of addition is subtraction

5.

Which calculation could you use to check that 15 + 8 = 23 is correct?

23 + 8 = 15

23 + 15 = 8

15 - 8 = 23

23 - 8 = 15

If a group of 15 and a group of 8 are combined, taking one group away again should leave you with the other

6.

If 29 - 15 = 14, what could you do to check the answer?

Subtract the numbers in a different order

Add 15 and 14 together

Take out any harder numbers

Put 14 at the beginning of the calculation

You can use addition to check a subtraction

7.

Use number pairs, or bonds, to 20 to find the incorrect calculation:

20 - 10 = 20

20 - 0 = 20

20 - 15 = 5

20 - 19 = 1

20 + 10 would not give a total of 20

8.

How would you check 45 - 23 = 22?

By subtracting 22 from 23

By adding 45 and 22

By finding the total of all the numbers

By adding 23 and 22

Adding the two smaller numbers should give the larger number

9.

If 3 + 4 + 10 + 3 = 20, what could you do to check the answer?

Take out all the larger numbers

Use multiplication

Add some extra numbers in too

Add the numbers up again in a different order:

10 + 3 + 3 + 4 or 10 + 4 + 3 + 3

10 + 3 + 3 + 4 or 10 + 4 + 3 + 3

Addition can be done in any order

10.

Use number pairs, or bonds, to 20 to find the incorrect calculation:

20 - 13 = 7

20 - 8 = 12

20 - 16 = 14

20 - 2 = 18

16 + 14 gives a total of 30, not 20

The next step is:

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