Latest Gate Aptitude Question SOLUTION: Two pipes – A and B – can fill a cistern in 20 min and 30 min respectively. A tap C can empty the cistern in 25 min. If A, B and C are opened in that order with a time gap of 2

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(#M40032743) GATE Numerical Ability question pipes and cisterns Keep an EYE

Two pipes – A and B – can fill a cistern in 20 min and 30 min respectively. A tap C can empty the cistern in 25 min. If A, B and C are opened in that order with a time gap of 2 minutes each, how long will it take for the cistern to be full?

a.18+2/3
b.20+12/13
c.16+12/13
d.none

Asked In Gate DHAKAD NEETENDRA SINGH (10 years ago)

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Durgesh Kumar Jaiswal  (10 years ago)

b is correct.

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Vivek Jain  (10 years ago)

Rate of flows:
Pipe A = 1/20
Pipe B = 1/30
Pipe C = 1/25 (used for emptying so -1/25)
now the order timeline for opening of pipes and tap are as follows:
[A] ---(2min)----> [B] ----(2min)---> [C] ------(T)------> FullCistern
So,
(T+4)/20 + (T+2)/30 - T/25 = 1
:: T= 16 12/13
Option C is correct

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