Water flows at 15 km/h through a pipe of internal diameter 14 cm into a rectangular tank 50 m long and 44 m wide. How long will it take for the water level in the tank to rise by 21 cm? Take $\pi = \frac{22}{7}$.

Explanation

1. 01

   Pipe radius = 7 cm = 0.07 m. Each hour a 15,000 m length of water flows in: $\frac{22}{7} \times 0.07 \times 0.07 \times 15{,}000 = 231$ m³.

2. 02

   Water needed = $50 \times 44 \times 0.21 = 462$ m³.

3. 03

   Time = $462 \div 231 = 2$ hours.