Algebra
Direct & inverse proportion
Twice the input, twice (or half) the output — two flavours of proportion.
Direct: y goes up as x goes up. Inverse: y goes down as x goes up.
Two forms
- Direct: y = kx (constant ratio).
- Inverse: y = k/x (constant product).
Try it
Speed × time = distance. Fixed distance — what kind of relationship?
Inverse: as speed goes up, time goes down.