Math Help - Find the rate of change

1. Find the rate of change

Hi,

I'm having problems understanding where to begin with this problem. Could someone here please point me in the right direction?

2. Re: Find the rate of change

We are given:

$V=\frac{1}{3}\pi r^2h$

and $h=3r$ so we may write:

$V=\frac{1}{3}\pi r^2(3r)=\pi r^3$

Now, implicitly differentiate with respect to time $t$, then use the values given for $\frac{dr}{dt}$ and $r$ to find $\frac{dV}{dt}$