An Introduction to Direct and Inverse Proportion
In mathematics and the physical sciences, direct proportionality is a relationship between two variables such that the ratio of the two variables is constant. If one variable is increased while the other is held constant, the value of the first variable will also increase. Inverse proportionality is a relationship between two variables such that the ratio of the two variables is inverse (or opposite) to each other. If one variable is increased while the other is held constant, the value of the first variable will decrease.