Originally Posted by

**Velmahr** Here's the question I have:

The radius of a sphere is increasing at a constant rate of 2cm/sec. At the instant when the volume of the sphere is increasing at 32pi cm^3/sec, the surface area of the sphere is

A) 8pi

B) 32pi/3

C) 16pi

D) 64pi

E) 256pi/3

So far I have dr/dt=2, and when dv/dt=32, SA=?

V=4/3pir^3

SA=4pir^2

I'm not sure how to relate these two equations. I assume I would solve for the radius of the sphere first, by finding the derivative of the Volume equation: dv/dt=4pir^2dr/dt, but I don't know what to do after that.