Question

Suppose that the water level of the conical paper cup that is 15 cm and a 5 cm radius is rising at 4 cm/s. How fast is the water being poured into the cup when the water is 8 cm deep?

Answer 1

looking for dV/dt
given dh/dt = 4
and h = 8

V = 1/3 pi r^2 h
take derivative -> dV/dt = 2/3 pi r (dr/dt) (dh/dt)

I'm stuck there because I don't know dr/dt :/