3.1(c) Variations (Direct and Inverse)

(c) Variations

(i) Direct Variation

If two quantities are related in such a way that increase (decrease) in one quantity causes increase (decrease) in the other quantity is called direct variation.

If a quantity $y$ varies directly as $x$ , then we write

$y\propto x$ i.e., $y = kx$

Where $k\neq 0$ is constant of variation.