Question

An expanding sphere has a radius r = 0.4t cm at time t (in seconds). Let V be the sphere's volume. Find dV/dt when (a) r=3 and (b) t=3

What is a

Answer 1

r=.4t ? are you giving dr/dt ?

Answer 2

No that's just how the book words it I think.

Answer 3

dr/dt = .4

Answer 4

That's what I got. but here are my choices


1.6π
3.2π
9π
9.1π
14.4π
21.1π