#### 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.

1. GENERAL RULE:
Round numbers to 1 significant figure

• 7.88
• 1820
• 3.65 × 10-44 × 10-4
• 10801000
2. EXCEPTIONS:
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

## 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.