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GCSE Maths / Edexcel

Rounding, estimation, and bounds overview

Recognise which rounding instruction a question is using, then choose the right focused lesson for practice.

Number and Place ValueFoundation and HigherGrades 3 to 7Overview

Curriculum path: GCSE Maths > Edexcel > Number > Rounding, estimation, and bounds

Pearson Edexcel GCSE Maths number: round numbers, estimate answers, and use limits of accuracy.

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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

Rounding means replacing a number with a nearby number that is easier to read or use. The question will tell you the accuracy it wants.

If the question says nearest 10, 100, 1000, or nearest whole number, it is asking for place-value rounding.

If the question says 1 decimal place or 2 decimal places, count digits after the decimal point.

If the question says significant figures, start counting from the first non-zero digit.

If the question says estimate, round the numbers first so the calculation is easier.

If the question says bounds, use half of the rounding step to find the smallest and largest possible original values.

Use this page as the overview. For careful practice, use the separate rounding, estimation, and bounds lessons in the Number and Place Value topic.

Key ruleRead the instruction first: nearest place value, decimal places, significant figures, estimate, or bounds.

Worked examples

Choosing the method

Which skill is needed for: round 3476 to the nearest 100?

  1. The phrase nearest 100 tells you this is place-value rounding.
  2. Use the hundreds digit and look at the tens digit.
  3. The focused lesson is rounding to nearest 10, 100, and 1000.

Answer: Place-value rounding

Decimal places or significant figures

What is the difference between 2 decimal places and 2 significant figures?

  1. Decimal places count digits after the decimal point.
  2. Significant figures count important digits from the first non-zero digit.
  3. For 0.04783, 2 decimal places is 0.05, but 2 significant figures is 0.048.

Answer: They count from different places

Bounds clue

A value is 70 to the nearest 10. What clue tells you this is a bounds question?

  1. The value has already been rounded.
  2. Bounds asks what original values could have rounded to 70.
  3. Nearest 10 has a half-step of 5, so the interval goes from 65 to 75.

Answer: The value has already been rounded

Common mistakes

  • Treating decimal places and significant figures as the same instruction.
  • Starting significant figures from zeros at the start of a decimal.
  • Using exact calculator work when the question asks for an estimate.
  • Using 0.5 as the half-step for every bounds question.
  • Forgetting that the upper bound is not included in an error interval.

Quick exercise

Try these before moving to the exam-style questions.

  1. Which skill is used for nearest 100?
  2. Which skill counts digits after the decimal point?
  3. Which skill starts from the first non-zero digit?
  4. Which skill uses easy rounded numbers before calculating?
  5. Which skill gives a lower and upper possible value?
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-calculator3 marks

For each instruction, name the skill being tested: (a) round to the nearest 10, (b) round to 2 decimal places, (c) round to 2 significant figures.

rounding methodsfoundation roundingexam language
Standard exam styleFoundation and HigherNon-calculator3 marks

Round 37.486 to (a) the nearest 10, (b) 1 decimal place, and (c) 2 significant figures.

mixed roundingnearest 10decimal placessignificant figures
ChallengeHigherCalculator4 marks

A rectangle has length 12.4 cm to the nearest 0.1 cm and width 5.8 cm to the nearest 0.1 cm. Find the upper bound for its area.

boundsupper boundareahigher reasoning