## anonymous 5 years ago 8. Sand pours from a chute and forms a conical pile whose height is always 2 times the base radius. If the base radius of the pile increases at a rate of 7 feet/hour, find the rate of change of the volume of the conic pile, when the base diameter of the pile is 10 feet.

1. anonymous

wait for a while. i'm solving it.

2. anonymous

$V=1/3\pi r ^{2}h$ $dv/dt=1/3\pi rdr/dt (2)h$ $dv/dt=2/3\pi r dr/dt h$ r=5,h=10, dr/dt=7ft/hr. $dV/dt=(700\pi)/3$

3. anonymous

the unit is feet per hour.

4. anonymous

i hope this can help.