Direct Proportion Graph
y = kx
ā¢ Straight line
ā¢ Passes through origin (0,0)
ā¢ Gradient = k
ā¢ As x doubles, y doubles
ā¢ As x halves, y halves
Inverse Proportion Graph
y = k/x
ā¢ Curved line (hyperbola)
ā¢ Never touches axes
ā¢ xy = k (constant)
ā¢ As x increases, y decreases
ā¢ As x doubles, y halves
Finding the Constant k
Direct: k = y/x
Inverse: k = xy
Use any known pair (x,y)
Then apply to find unknowns
This diagram covers Visual Understanding 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 6 of 16 in this topic. Focus on the labels, the relationships between parts, and the explanation that turns the diagram into an exam-ready answer.
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.