Question

The water in a rectangular reservoir has a base 80 m × 60 m and is 6.5 m deep. In what time(in hours) can the water be emptied by a pipe having a cross section in the form of a square of side 20 cm, if water runs through the pipe at the rate of 15 km/ hr?

• A. 50
• B. 40
• C. 52
• D. 42

Answer 1

The correct option is C

52

Volume of water in the reservoir
= (80 × 60 × 6.5) m${}^3$
= 31200 m${}^3$
Side of square = 20 cm = 0.2 m
$\therefore$ Its area = 0.04 m${}^2$
Rate of flow of water = 15 km/hr = 15000 m/hr
The volume of the water emptied in 1 hour
= 15000 x 0.04
= 600 m${}^3$
Hence, the time taken to empty the reservoir
= $\frac{31200}{600}$
= 52 hours