A Spherical Raindrop Evaporates at a Rate Proportional to Its $V=\frac{4}{3} \pi r^{3}$

Short Answer

A spherical raindrop evaporates at a rate proportional to its surface area.Let V = volume of the raindrop and S = surface area.For a sphere, $V=\frac{4}{3} \pi r^{3}$ and $S=4 \pi r^{2}$ .If it takes 6 minutes for a spherical raindrop to evaporate to $\frac{1}{8}$ of its original volume, how many minutes will it take to completely evaporate?