## College Algebra 7th Edition

$s\approx 46\$mi/h
Since $D$ varies directly as the square of the speed $s$, we have: $D=ks^{2}$ We are given: $D=150$ and $s=40$, so we have: $150=k(40)^{2}$ $k=0.09375$ Therefore: $D=0.09375s^{2}$ If we plug in $D=200$, we can find $s$: $200=0.09375s^{2}$ $s=\sqrt{200/0.09375}$ $s\approx 46\$mi/h