calculus math202

Question

As a snowball melts, its area A decreases at the rate 3 cm²/minute. Find the rate with which it radius decreases, when the radius r=3 cm. Use that the surface area of a sphere is given by the formula A=4πr² (where π is approximately 3.1415926535). Enter your answer as a number only, correct to at least four decimal places, no sign. 

Answer 1

A = 4πr² 

Find the derivate of the area with respect to time (d/dt)

dA/dt = 8πr(dr/dt)

r = 3

dA/dt = -3

Plug in values and evaluate.