## College Algebra (11th Edition)

$r=\frac{d}{t}$, means that $r$ varies directly with $d$ and also $r$ varies inversely with $t$.
The general equation for direct variation is $y=kx$, where k is the constant of the variation. The general equation for inverse variation is $y=\frac{k}{x}$, where k is the constant of the variation. Here, $r=\frac{d}{t}$, means that $r$ varies directly with $d$ and also $r$ varies inversely with $t$. As d is the nominator, there will be a direct variation between $r$ and $d$, as t is in the denominator, there will be an inverse variation between $r$ and $t$ As none of $d$ or $t$ is constant, there isn't any constant in these variations. Therefore we can say that the speed varies directly with the distance traveled and varies inversely with the time needed.