Direct Proportion Examples
- Distance ∝ Time (constant speed)
- Cost ∝ Quantity (fixed price per unit)
- Perimeter ∝ Side length (similar shapes)
- Wages ∝ Hours worked (hourly rate)
Inverse Proportion Examples
- Speed ∝ 1/Time (fixed distance)
- Workers ∝ 1/Time (fixed job)
- Brightness ∝ 1/Distance² (light intensity)
- Pressure ∝ 1/Volume (gas laws)
This exam tips covers Real-World Applications within Proportion for GCSE Mathematics. Revise Proportion in Number for GCSE Mathematics with 12 exam-style questions and 22 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 13 of 16 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Practice questions for Proportion
y is directly proportional to x. Which equation could represent this relationship?
Explain how you can tell from a graph whether two quantities are in direct or inverse proportion.
Quick recall flashcards
Proportion Symbol
∝ means 'proportional to'
Examples:
y ∝ x (y is proportional to x)
y ∝ 1/x (y is inversely proportional to x)
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