Inverse proportion
y = k/x. Doubling x halves y. Higher: y ∝ 1/x&sup{n}.
Inverse proportion: as one quantity grows the other shrinks proportionally. y = k/x or equivalently xy = k.
Worked examples
4 painters take 6 days: workers×days = 24. 8 painters take 3 days.
If y = 5 when x = 4, then xy = 20 and y = 20/x.
Inverse-square: y ∝ 1/x². Light intensity from a point source.
Frequently asked questions
How to spot?
‘The product is constant’ or ‘more workers means fewer days’.
Equation form?
y = k/x. Find k from a given pair, then use the formula for new values.