Question

The water in a rectangular reservoir having a base $80m$ by $60m$ is $6.5m$ deep. In what time can the water be emptied by a pipe of a square cross-section is of side $20cm$, if the water runs through the pipe at the rate of $15km$ per hours?

• A. $26$ hours
• B. $42$ hours
• C. $52$ hours
• D. $65$ hours

Answer 1

The correct option is C $52$ hours

The reservoir is in the shape of a cuboid.

Volume of water in the reservoir in $=80\times 60\times \frac{13}{2}{m}^3=31200m^3$

Volume of water flown in $1$ hour $=$ Speed $\times$ Area of the cross section

$=15\times 1000\times \frac{20}{100}\times \frac{20}{100}=600m^3$

Time taken to empty $31200m^3=\frac{31200}{600}=52$ hours