Question

If a snowball melts so that its surface area decreases at a rate of 4 cm2/min, find the rate at which the diameter decreases when the diameter is 9 cm.

Answer 1

SA = 4πr^2
d(SA)/dt = 8πr dr/dt

for the given data

4 = 8π(4/5) dr/dt
dr/dt = ....

d(diameter)/dt = 2 dr/dt

Answer 2

.1990