Question

A cuboidal reservoir of base $80m\times 60m$ is $6.5m$ 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 $20cm,$ if water runs through the pipe at the rate of $15km/hr?$

• A. 50 hours
• B. 55 hours
• C. 52 hours
• D. 48 hours

Answer 1

The correct option is C

52 hours

Volume of water in the reservoir $=80\times 60\times 6.5=31200m^3$

Area of the cross-section of the square pipe $=20\times 20=400c{m}^2$

Volume of the water emptied in one hour $=400c{m}^2\times 15km/hr$

$=0.04\times 15000=600m^3$
Time taken to empty the reservoir $=\frac{\text{Volume of water in the reservoir}}{\text{Volume of water emptied in one hour}}=\frac{31200}{600}=52$ hours