OPERATIONS

Mental Subtraction

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

1 · WHAT YOU NEED TO KNOW

The idea

Accurate arithmetic keeps each digit in its correct place-value column.

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. Align equal place values.
  2. Calculate from right to left, regrouping when necessary.
  3. Estimate first and use the inverse operation to check the result.
3 · WORKED EXAMPLES

See the method in action

Example 1

Calculate 829 - 414 mentally by compensating.

  1. Subtract 417, then add 3: 829 - 417 + 3 = 415.
Answer: 415
Example 2

A stadium has 1010 seats. 391 are occupied and 179 are reserved. How many remain available?

  1. Subtract the occupied seats: 1010 − 391 = 619.
  2. Then subtract the 179 reserved seats, leaving 440.
Answer: 440
4 · ELEVENSPRINT TIP

A useful shortcut

Estimate first and use the inverse operation to check 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.