inverse proportion

Inverse proportion is the relationship between two quantities. As one quantity increases the other quantity decreases, or vice versa.

An example of inverse proportion is the length and width of rectangles which have the same area.

If the length of one side of a rectangle doubles, the width has to be halved for the area to stay the same.

This is shown in the diagram opposite.

Another example is machines which fulfil a specific role. As the number of machines (x) which do the work increases, the time they take (y) decreases. The graph opposite shows this. This relationship can be written as y ∝ 1/x which is expressed in words as ‘y is inversely proportional to x‘.