# Connected Rates of change question

• Feb 20th 2009, 10:06 AM
Big_Joe
Connected Rates of change question
This is the question:

A cone has height 6 cm. The radius of the base of the cone is increasing at 5cm/s. Find the rate of change of the volume of the cone when the radius of the base is 4cm.

I have already worked out that the current volume of the cone is equal to 32 pi but i dont know where to go from here.

Thanks in advance to anyone that helps!
• Feb 20th 2009, 11:28 AM
Rist
You need to find $\frac{dr}{dt}$ and $\frac{dV}{dr}$, then multiply them to get $\frac{dV}{dt}$ that you need. Answer is $80\pi$