1.60: Related Rates for a Circular Pool

Oil leaking from a pipeline forms a circular pool on the ground. The area of the pool increases at a constant rate of $\displaystyle 8\,\mathrm{cm}^2/\mathrm{s}$.

Find the rate of increase of the radius of the pool, in $\displaystyle \mathrm{cm}/\mathrm{s}$ to 3 significant figures, at the instant when the area of the pool is $\displaystyle 50\,\mathrm{cm}^2$.