OPERATIONS

Inverse Operations

Learn the reliable method for inverse operations, then apply it to 11+ exam-style questions.

1 · WHAT YOU NEED TO KNOW

The idea

Inverse operations undo one another and can recover or check a missing value.

Picture itLine up the operation one step at a time
Bowls, fruit, scales and a measuring jug showing ratio and measurement in baking
2 · THE METHOD

Follow these steps

  1. Identify the operations already applied.
  2. Undo them in reverse order.
  3. Run the original operations forward to verify the result.
3 · WORKED EXAMPLES

See the method in action

Example 1

184 counters are shared equally between 8 bags. How many counters go in each bag?

  1. 184 ÷ 8 = 23 counters in each bag.
Answer: 23
Example 2

A number is multiplied by 6, then 9 is added, giving 165. What was the number?

  1. Undo the addition: 165 − 9 = 156.
  2. Then divide: 156 ÷ 6 = 26.
Answer: 26
4 · ELEVENSPRINT TIP

A useful shortcut

Run the original operations forward to verify the result.

5 · COMMON MISTAKES

Watch out for these

6 · TRY IT YOURSELF

Three fresh questions

Ready to check the method? You will get three fresh, validated questions.