## College Algebra (11th Edition)

$d$ varies directly with $s$ and the constant of this variation is $\frac{1}{5}$.
The general equation for direct variation is $y=kx$, where k is the constant of the variation. Here, $d=\frac{1}{5}s$, means that $d$ varies directly with $s$. The equation for direct variation here, is $d=k\times s$ As $\frac{1}{5}$ is constant, this will be the constant of the variation. Therefore the distance from a storm varies directly with the time between seeing lightning and hearing thunder, and the constant of this variation is $\frac{1}{5}$.