Answer
15 mi/hr
Work Step by Step
We know that if point $P$ is a point on a circle of radius $r$, and $P$ moves in a distance $s$ on the circumference of the circle in an amount of time $t$, then the linear velocity, $v$, of $P$ is calculated as $v=\frac{s}{t}$.
We are given that $s=30$ mi and $t=2$ hr.
Therefore, $v=\frac{30mi}{2hr}=\frac{30mi\div2}{2hr\div2}=\frac{15mi}{1hr}=15$ mi/hr.