Cambridge O Level Mathematics (Syllabus D) · Syllabus 4024 · Algebra and Graphs
Proportion
What is Proportion?
A relationship in which one quantity is a fixed multiple of a power or root of another. In direct proportion the two quantities rise and fall together and y equals k times that power; in inverse proportion one rises as the other falls and y equals k divided by that power. The symbol for is proportional to must be replaced by an equals sign and a constant of proportionality k before any calculation, and k is found by substituting one given pair of values.
This definition is part of the Algebra and Graphs chapter in Cambridge O Level Mathematics (Syllabus D).
Proportion in context
Every proportion question, without exception, is the same three moves: write the equation with \(k\), find \(k\) from the pair of values you were given, use the completed formula to answer the question. The only thing that changes between questions is which power sits in the equation. Learn the three moves and the topic collapses to a single routine.