## Calculus (3rd Edition)

Volume V= Base area $\times$ Height $=18\,ft^{2}\times h$ $\frac{dV}{dh}=\frac{d}{dh}(18\,ft^{2}\times h)= 18\,ft^{2}$ $\frac{dV}{dt}=0.7 ft^{3}/min$ $\frac{dh}{dt}=\frac{\frac{dV}{dt}}{\frac{dV}{dh}}=\frac{0.7\,ft^{3}/min}{18\,ft^{2}}= 0.039\,ft/min$