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Ratio & ProportionIntroduction

What Is Direct Proportion?

Part of Proportion Graphs — GCSE Mathematics

This introduction covers What Is Direct Proportion? within Proportion Graphs for GCSE Mathematics. Revise Proportion Graphs in Ratio & Proportion for GCSE Mathematics with 14 exam-style questions and 4 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 1 of 5 in this topic. Use this introduction to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 1 of 5

Practice

14 questions

Recall

4 flashcards

What Is Direct Proportion?

If you buy 2 pizzas for £10, 4 pizzas cost £20, and 6 pizzas cost £30. Double the pizzas = double the price. This is direct proportion! When one quantity doubles, the other doubles too. The ratio between them stays CONSTANT.

Keep building this topic

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

Key FactsMethod: Finding the ConstantWorked Example 1: Basic Direct Proportion

Practice Questions for Proportion Graphs

Which of the following describes the graph of a direct proportion relationship?

  • A. A curved line passing through the origin
  • B. A straight line passing through the origin
  • C. A straight line that crosses the y-axis above zero
  • D. A U-shaped curve symmetric about the y-axis
1 markfoundation

Aisha says: 'Because the graph of y against x is a straight line, y must be directly proportional to x.' Is Aisha correct? Explain your answer.

2 marksstandard

Quick Recall Flashcards

Finding k
Use given values to find constant k, then apply to new values
Direct vs Inverse
Direct: both increase together (y ∝ x). Inverse: one increases, other decreases (y ∝ 1/x).

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