I was given this question, but was unable to figure out how to solve it as I was given very few values:
Assume that oil spilled from a ruptured tanker forms a circular oil slick whose radius increases at a constant rate of $0.42$ feet per minute. Estimate the rate at which the area of the spill is increasing when the diameter of the spill is $240$ feet.
(I was also supposed to leave the answer in terms of $\pi$).
However, I don't know where to start. I know that I am solving for $\frac{dA}{dt}$ and radius = $120$ as well as $\frac{dr}{dt} = 0.42$, but that is it. Does anyone have any hints for me? (I don't want a full solution just hints as to how I can better understand)