Discussion of Question with ID = 055 under Pipes-and-Cisterns

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Question

Two pipes, A and B, can fill a cistern in 5 and 8 mins respectively. There is a leakage tap that can drain 8 liters of water per minute. If all three of them work together, the tank is filled in 15 minutes. What is the volume of the tank?

A

$30{30/31}$ liters.

B

$33{1/30}$ liters.

C

$28{5/33}$ liters.

D

$31{10/11}$ liters.

Soln.
Ans: a

Work done by the leakage in 1 min is $1/5 + 1/8 - 1/15$ = ${31/120}$. This work is equivalent to a volume of 8 liters. So, the total volume is 8 × ${120/31}$ = ${960/31}$, which is same as: $30{30/31}$ liters.


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