Ratio & ProportionKey Facts

Key Features of Direct Proportion

Part of Direct Proportion — GCSE Mathematics

This key facts covers Key Features of Direct Proportion within Direct Proportion for GCSE Mathematics. Revise Direct Proportion in Ratio & Proportion for GCSE Mathematics with 15 exam-style questions and 12 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 2 of 8 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 8

Practice

15 questions

Recall

12 flashcards

Key Features of Direct Proportion

We write y ∝ x to mean "y is directly proportional to x"

This means y = kx where k is a constant

Feature	What it means
Graph shape	Straight line through the origin (0,0)
When x doubles	y also doubles
Ratio y/x	Always the same (equals k)
The constant k	k = y ÷ x (the gradient of the line)

Practice Questions for Direct Proportion

Which of the following correctly reads the mathematical statement y ∝ x?

A. y is inversely proportional to x
B. y is directly proportional to x
C. y equals x
D. y is greater than x

1 markfoundation

Explain what it means for y to be directly proportional to x. Your answer should refer to the equation and the graph.

2 marksstandard

Quick Recall Flashcards

What does the graph of y = kx look like?

A straight line passing through the origin (0, 0). The gradient of the line equals k. If the line does NOT pass through (0,0), it is NOT direct proportion.

What does the symbol ∝ mean?

'is proportional to' y ∝ x means 'y is proportional to x' This is equivalent to writing y = kx for some constant k.

Key Features of Direct Proportion

Key Features of Direct Proportion

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Practice Questions for Direct Proportion

Quick Recall Flashcards

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