What is it
Proportion covers direct proportion (two quantities increase together at a constant rate) and inverse proportion (as one quantity increases, the other decreases), including writing and solving proportion equations.
Why it matters
Proportion reasoning appears in real contexts throughout GCSE and beyond — from recipe scaling to speed, distance and time problems — and Higher tier questions often expect you to write a formal proportion equation rather than just reason informally.
Exam tip
Write 'y is proportional to x' as y = kx before substituting known values to find k — this formal approach is required for full marks on Higher tier proportion questions, even when the informal method gives the right answer.
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