Gravel is being dumped from a conveyor belt at a rate of 30 ft3/min. It forms a pile in the shape of a right circular cone whose base diameter and height are always the same. How fast is the height of the pile increasing when the pile is 21 ft high?

Answer 1

so h = r

V = (1/3)πr^2 h ---- #1
V = (1/3)π h^3

dV/dt = π h^2 dh/dt ----- #2

you have all the values of #2 except dh/dt
Go for it