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GCSE Mathematics · key term
A value close to an exact value, chosen to make a calculation easier or to show its likely size.
Used by AQA, Edexcel and OCR
Specification N14 · Paper 1, Paper 2, Paper 3
A value used in place of another value because it is sufficiently close for the purpose.
Revise: EstimationGood estimation is about choosing approximations fit for the calculation, not applying a rule mechanically.
Specification N14 · Paper 1, Paper 2, Paper 3
Replacing a number with a nearby, easier number to make a calculation simpler.
Show the approximations you use before calculating; an unsupported decimal is not clearly an estimate.
Use when replacing a value or expression by an approximation. Use only for steps that are exactly equal.
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Choose approximations that keep the important size of each number.
Specification 3.03a, 4.01b · Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Foundation), Paper 4 (Higher), Paper 5 (Higher), Paper 6 (Higher)
A decimal value close to an exact value but not necessarily equal to it, usually produced by rounding.
One significant figure often makes mental arithmetic convenient, but choose different approximations if they produce a simpler or more useful calculation.