A = 4πr^2
dA/dt = 8πr dr/dt
when d = 8, r = 4, dA/dt = -2
-2 = 8π(4)dr/dt
dr/dt = -1/(16π)
so dd/dt = -1(8π) cm/min
A spherical snowball is placed in the sun. The snowball melts so that it's surface area
decreases at a rate of 2 cm2
/min. Find the rate at which the diameter decreases when the
diameter is 8 cm
1 answer