AAAarubi AcademyGCSE Maths Edexcel first
Join nowSign in
GCSE Maths / Edexcel

Estimation

Round values to easy numbers before calculating so you can estimate answers and check reasonableness.

Number and Place ValueFoundation and HigherGrades 3 to 6Focused skill

Curriculum path: GCSE Maths > Edexcel > Number > Estimation

Pearson Edexcel GCSE Maths number: estimate answers and check calculations using approximation.

Practise this topicUpload your answerAsk AI to explain thisTry exam-style questions
Revision notes

Theory, examples, and quick checks.

Keep the method short, then practise straight away. This note is written for GCSE Maths Edexcel students who need clear working and reliable method marks.

Theory

Estimation means finding an approximate answer, not an exact answer.

The purpose is to check whether a calculator answer or written calculation is sensible.

Round each number to something easy to calculate mentally. Often this means 1 significant figure, but choose numbers that make the calculation simple.

For multiplication and division, choose numbers that are easy to multiply or divide.

An estimate does not have to be exact, but it should be close enough to show the size of the answer.

If the exam says estimate, show the rounded numbers first. This is where method marks usually come from.

Key ruleRound first, calculate second, then check if the answer is sensible.

Worked examples

Multiplication estimate

Estimate 48.7 x 19.8.

  1. 48.7 is close to 50.
  2. 19.8 is close to 20.
  3. 50 x 20 = 1000.

Answer: 1000

Division estimate

Estimate 398 / 19.7.

  1. 398 is close to 400.
  2. 19.7 is close to 20.
  3. 400 / 20 = 20.

Answer: 20

Fraction-style estimate

Estimate (61.2 x 4.8) / 0.51.

  1. 61.2 is close to 60.
  2. 4.8 is close to 5.
  3. 0.51 is close to 0.5.
  4. (60 x 5) / 0.5 = 300 / 0.5 = 600.

Answer: 600

Common mistakes

  • Using exact calculator work when the question asks for an estimate.
  • Rounding numbers in a way that makes the calculation harder.
  • Rounding a decimal such as 0.51 to 1 when 0.5 would make more sense.
  • Forgetting that dividing by 0.5 doubles the number.

Quick exercise

Try these before moving to the exam-style questions.

  1. Estimate 39.6 x 5.2.
  2. Estimate 198 / 9.8.
  3. Estimate 52 x 31.
  4. Estimate 6.1 x 19.7.
  5. Estimate 297 / 0.98.
Exam-style questions

Practise the same skill at three levels.

These are original GCSE-style questions with mark schemes, common wrong answers, and AI marking guidance so feedback stays close to exam expectations.

Basic GCSE styleFoundationNon-calculator2 marks

Estimate 31.2 x 19.6.

estimationmultiplicationfoundation number
Standard exam styleFoundation and HigherNon-calculator3 marks

Estimate the value of (61.2 x 4.8) / 0.51.

estimationdivision by decimalsnumber sense
ChallengeHigherCalculator4 marks

A student calculates 49.8 x 0.196 and gets 976.08. Use estimation to explain why this answer cannot be correct.

checking answersestimationreasoning