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Year 2 Calculation - Inverse Operations
To check if 4 + 1 = 5 you could try seeing if 5 - 1 = 4 or 5 - 4 = 1.

Year 2 Calculation - Inverse Operations

Use inverse operations to check answers. Switch between addition and subtraction to spot mistakes and build confident mental methods.

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Fascinating Fact:

Check addition with subtraction: 28 + 6 = 34? Try 34 − 28. It is 6, so the sum is correct.

In KS1 Maths, Year 2 pupils learn to use inverse operations to check their work. If you add to get an answer, you can subtract to see if you return to the start number.

  • Inverse: An opposite operation that undoes a calculation, like addition and subtraction.
  • Fact family: A set of linked addition and subtraction facts that use the same numbers.
  • Check: A quick test using the inverse to confirm your answer makes sense.

Warm up with quick number checks: try the Numeracy Game before you start the quiz.

What are inverse operations in Year 2?

Inverse operations are opposite operations that undo each other. In Year 2, we use addition with subtraction to check answers quickly.

How do I check an addition using the inverse?

Take the total and subtract one of the addends. If the result is the other addend, your addition is correct. Example: 19 + 4 = 23, check 23 − 19 = 4.

What is a simple fact family example?

For the numbers 7, 5, and 12: 7 + 5 = 12, 5 + 7 = 12, 12 − 7 = 5, 12 − 5 = 7. These four facts belong together.

Question 1
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
Question 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
If a group of 15 and a group of 8 are combined, taking one group away again should leave you with the other
Question 3
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
Question 4
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
Addition can be done in any order
Question 5
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
Question 6
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
Question 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
You can use addition to check a subtraction
Question 8
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
Question 9
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
Question 10
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
Author:  Angela Smith (Primary School Teacher & KS1 Quiz Writer)

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