The surface area of a sphere is decreasing at the constant rate of 3*pi sq. cm/sec . ? at what rate is the volume of the sphere decreasing at the instant its radius is 2 cm ?

Surface area of a sphere:
Volume of a sphere:

Differentiate both with respect to an arbitrary variable for time:



You're given that when , so you can use this in the first equation to solve for .



Now use this to find .

$18.25 ($365 divided by 20)