 # KS1 Maths Quiz - Year 2 Calculation - Inverse Operations (Questions)

This quiz addresses the requirements of the National Curriculum KS1 Maths and Numeracy for children aged 6 and 7 in year 2. Specifically this quiz is aimed at the section dealing with checking calculations using the inverse operation.

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!

1. 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
2. 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
3. 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
4. Use number pairs, or bonds, to 20 to find the incorrect calculation:
 [ ] 20 - 13 = 7 [ ] 20 - 8 = 12 [ ] 20 - 16 = 14 [ ] 20 - 2 = 18
5. Use number pairs, or bonds, to 20 to find the incorrect calculation:
 [ ] 20 - 10 = 20 [ ] 20 - 0 = 20 [ ] 20 - 15 = 5 [ ] 20 - 19 = 1
6. 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
7. 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
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
9. 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
10. What does 'inverse operation' mean?
 [ ] Doing the calculation upside down [ ] Making a mistake on purpose [ ] The opposite operation [ ] A medical procedure KS1 Maths Quiz - Year 2 Calculation - Inverse Operations (Answers)
1. Which calculation could you use to check that 16 - 9 = 7 is correct?
 [ ] 16 + 9 = 7 [x] 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
2. Which calculation could you use to check that 15 + 8 = 23 is correct?
 [ ] 23 + 8 = 15 [ ] 23 + 15 = 8 [ ] 15 - 8 = 23 [x] 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
3. How do you know that 20 - 10 = 10?
 [x] 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
4. Use number pairs, or bonds, to 20 to find the incorrect calculation:
 [ ] 20 - 13 = 7 [ ] 20 - 8 = 12 [x] 20 - 16 = 14 [ ] 20 - 2 = 18
16 + 14 gives a total of 30, not 20
5. Use number pairs, or bonds, to 20 to find the incorrect calculation:
 [x] 20 - 10 = 20 [ ] 20 - 0 = 20 [ ] 20 - 15 = 5 [ ] 20 - 19 = 1
20 + 10 would not give a total of 20
6. 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 [x] Add the numbers up again in a different order: 10 + 3 + 3 + 4 or 10 + 4 + 3 + 3
Addition can be done in any order
7. If 29 - 15 = 14, what could you do to check the answer?
 [ ] Subtract the numbers in a different order [x] 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
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 [x] By adding 23 and 22
Adding the two smaller numbers should give the larger number
9. How could you check 62 + 38 = 100?
 [ ] By taking away 100 [ ] By finding the difference between 62 and 38 [ ] By subtracting 100 from 62 [x] By subtracting 38 from 100
If 62 + 38 = 100 is correct, then 100 - 38 should give an answer of 62
10. What does 'inverse operation' mean?
 [ ] Doing the calculation upside down [ ] Making a mistake on purpose [x] The opposite operation [ ] A medical procedure
The inverse of subtraction is addition, the inverse of addition is subtraction