How fast is the water level rising when the water is 4 m deep?

Explanation

1. 01

   $V = \frac{\pi h^{3}}{12}$, so $\frac{dV}{dt} = \frac{\pi h^{2}}{4}\frac{dh}{dt}$.

2. 02

   $2 = \frac{\pi \times 16}{4}\frac{dh}{dt} = 4\pi\frac{dh}{dt}$, so $\frac{dh}{dt} = \frac{1}{2\pi}$ m/min.