NumberKey Facts

What is Proportion?

Part of ProportionGCSE Mathematics

This key facts covers What is Proportion? within Proportion for GCSE Mathematics. Revise Proportion in Number for GCSE Mathematics with 12 exam-style questions and 22 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 2 of 15 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 2 of 15

Practice

12 questions

Recall

22 flashcards

What is Proportion?

  • Definition: A relationship where one quantity changes in a predictable way when another changes
  • Direct proportion: Both quantities increase/decrease together
  • Inverse proportion: One increases as the other decreases
  • Symbol: ∝ means "is proportional to"
  • Constant: k is the constant of proportionality

Keep building this topic

Read this section alongside the surrounding pages in Proportion. That gives you the full topic sequence instead of a single isolated revision point.

Practice Questions for Proportion

y is directly proportional to x. Which equation could represent this relationship?

  • A. y = k/x
  • B. y = kx
  • C. y = k − x
  • D. y = x²
1 markfoundation

Explain how you can tell from a graph whether two quantities are in direct or inverse proportion.

2 marksstandard

Quick Recall Flashcards

Recipe Application
Recipe for 4 people uses 300g flour How much for 10 people? Flour ∝ People (direct) F = kP 300 = k × 4, so k = 75 For 10 people: F = 75 × 10 = 750g
Proportion Symbol
∝ means 'proportional to' Examples: y ∝ x (y is proportional to x) y ∝ 1/x (y is inversely proportional to x)

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