Water tank

The water tank has a cylindrical shape with a base diameter of 4.2 m and is 80 cm deep. How many minutes will it take to fill it 10 cm below the edge of the tank if water flows 2 liters per second?

Correct answer:

t =  80.8175 min

Step-by-step explanation:

$$\begin{gathered} D=42\text{dm} \\ h=(80-10)/10=7\text{dm} \\ r=D/2=42/2=21\text{dm} \\ V=\pi \cdot r^2\cdot h=3.1416\cdot 21^2\cdot 7\doteq 9698.0965{\text{dm}}^3 \\ v=2\cdot 60=120\text{l/min} \\ t=V/v=9698.0965/120=80.8175\text{min} \end{gathered}$$

Try another example