Approximation and Estimation

intermediate24 min read

When an exam question wants a close value rather than an exact one: rounding with the error kept small, approximating percentages, fractions, squares and roots, breaking a product into round numbers, and using the answer options to decide how rough you can be.

What you will be able to do

Round each term of an expression so the errors tend to cancel.
Approximate a percentage-of or fraction-of quickly.
Estimate a square, a square root and a large product.
Use the spacing of the answer options to judge how rough an estimate can be.

What is inside this lesson

1What the question asks, and the error budget
2Round so the errors cancel
3Percentages and fractions
4Squares, roots and products
5Worked example: a messy expression
6Worked example: percentage of a number
7Worked example: a square root
8Common mistakes
9Quick revision
10Practice

The lesson itself is for members

Reading the 10 sections above, the worked examples and the practice set is free — the whole knowledge base is on the free plan, along with flashcards, private notes and Ask Onely.

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