Checking a calculation and checking a solution are not the same. A numerical result can be correct yet fail to answer the question, omit a unit or make no sense in context.

Teach a concise final routine: Question. Complete. Unit. Reasonable.

Return to the original question

Ask the pupil to reread what was required and compare it with their final line.

• Did the problem ask for a total, difference, number of groups or amount remaining?

• Was there more than one part?

• Is the result an intermediate value rather than the final answer?

• Does the answer need rounding or interpretation?

The check should begin with meaning, not repeated calculation.

Check completeness

Look for whether:

• every stage has been completed;

• all conditions have been used;

• the final quantity is labelled;

• the unit is present;

• the answer is written in an appropriate form.

If a problem asks how many buses are needed for 93 pupils when each bus holds 40, the calculation 93 ÷ 40 = 2 remainder 13 is not the final answer. Three buses are needed.

Check reasonableness

Use a quick estimate or relationship:

• Should the answer be larger or smaller than the starting amount?

• Is it close to an estimated value?

• Is it possible in the context?

• Does the unit fit?

• Does the remainder need interpretation?

For three books at £4.75 each, an answer of £142.50 should be rejected because the expected total is near £15.

Keep the routine short

A pupil may use four brief questions:

1. What did I need to find?

2. Have I answered every part?

3. Is the unit or label correct?

4. Does the result make sense?

An oral check is often enough. Do not require a lengthy written explanation for every routine problem.

Find what needs revisiting

If the answer does not fit, locate the problem:

• interpretation;

• missing condition;

• representation;

• operation;

• calculation;

• unit;

• final statement.

Avoid restarting the entire solution when only the final interpretation is wrong.

Fade the prompt

Use the full four-question card during teaching, then reduce it to “question, unit, reasonable”. Later, pause before accepting the answer and allow the pupil to check independently.

Do not add a separate checking routine where the pupil already reviews answers accurately.

Common mistakes to avoid

• Checking only by recalculating.

• Accepting an unlabelled number.

• Ignoring a remainder in context.

• Requiring a long explanation after every answer.

• Restarting the whole problem without finding the faulty stage.

• Prompting when the pupil already checks independently.

• Treating an implausible result as a minor presentation issue.

Evidence and further reading

The Education Endowment Foundation’s article on using think-alouds in maths includes modelling how to monitor and check solutions. The national curriculum mathematics programmes of study require pupils to estimate, check and interpret answers in context.