Revision Notes

Why use estimation?

We ESTIMATE to find approximations for difficult sums or to check our answers are about the right size (right order of magnitude).

How to estimate

We ROUND numbers to something sensible before CALCULATING.

    Round numbers to 1 significant figure 

    • 7.88
    • 1820
    • 3.65 × 10-44 × 10-4
    • 10801000
    It can be more sensible (or easier) to round to something convenient

    • 16.215
    • 9.110
    • 11801200
    • It wouldn’t usually make sense to round a number to zero
  3. FRACTIONS get bigger when the top is bigger and/or the bottom is smaller and vice versa


Rounding & Estimation, IGCSE & GCSE Maths revision notes


Need help?

Edexcel GCSE Maths Notes

Want to aim for a Level 9?

See if you’ve got what it takes. Test yourself with our topic questions.

Author: Simon

After 24 years teaching A Level Further Maths, Maths whizz Simon focused his attention on tutoring. He’s helped thousands of young people make sense of Maths and now he’s helping you too – aren’t you lucky! He’s even worked as an Edexcel examiner, so knows exactly what they’re looking for.