What is the rate of change of its total surface area when its radius and height are 20 in and 50 in respectivley?

Question

What is the rate of change of its total surface area when its radius and height are 20 in and 50 in respectivley?

Answer 1

S=2πrh thus dS/dt=2πhdr/dt +2πrdh/dt. Substitute the values for r, h, dr/dt and dh/dt.