Inverse Operations
(KS2, Year 4)

The Lesson

An inverse operation is the opposite of an operation. It reverses an operation.

If the inverse operation reverses the operation, the operation reverses the inverse operation.

Addition and Subtraction

The inverse operation of addition is subtraction.

Imagine we add 2 to 3...
3 + 2 → 5
...we can reverse the operation by subtracting 2:
3 ← 5 − 2
Subtraction has reversed the addition. Subtraction is the inverse operation of addition...

...and Vice Versa

If subtraction is the inverse operation of addition, the inverse operation of subtraction is addition. Imagine we subtract 2 from 3...
3 − 2 → 1
...we can reverse the operation by adding 2:
3 ← 1 + 2
Addition has reversed the subtraction. Addition is the inverse operation of subtraction.

Multiplication and Division

The inverse operation of multiplication is division.

Imagine we multiply 4 by 2...
4 × 2 → 8
...we can reverse the operation by dividing by 2:
4 ← 8 ÷ 2
Division has reversed the multiplication. Division is the inverse operation of multiplication...

...and Vice Versa

If division is the inverse operation of multiplication, the inverse operation of division is multiplication. Imagine we divide 4 by 2...
4 ÷ 2 → 2
...we can reverse the operation by multiplying by 2:
4 ← 4 × 2
Multiplication has reversed the division. Multiplication is the inverse operation of division.

Squaring and the Square Root

The inverse operation of squaring is taking the square root.

Imagine we square 3...
32 → 9
...we can reverse the operation by taking the square root:
3 ← √9
The square root has reversed the squaring. The square root is the inverse operation of squaring...

...and Vice Versa

If the square root is the inverse operation of squaring, the inverse operation of the square root is squaring. Imagine we take the square root of 4...
4 → 2
...we can reverse the operation by squaring:
4 ← 22
Squaring has reversed the square root. Squaring is the inverse operation of the square root.

Lesson Slides

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Why Is an Inverse Operation Useful?

Checking Your Answer

The inverse operation is useful for checking your answers. Imagine you multiply 6 by 4:
6 × 4 = 24
The inverse operation of multiplication is division. Divide your answer by 4 to see if you get back to 6:
24 ÷ 4 = 6

Top Tip

Inverse Operations

The inverse operations are summarised below:

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See Also

How to add How to subtract How to multiply How to divide What is an square number? What is a square root?