Two pipes A and B can fill in 40 minutes and 30 minutes respectively Both the pipes are opened toget...........

Quantitative Aptitude ( CCS) Pipes&cistern

Two pipes A and B can fill in 40 minutes and 30 minutes respectively. Both the pipes are opened together but after 5 minutes, pipe B is turned off. What is the total time required to fill the tank ?

33 min. 20 sec.

35 min. 40 sec.

26 min. 32 sec.

38 min. 30 sec.

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Explanation:

Part filled in 5 minutes = 5(1/40 + 1/30) = 5*7/120 = 7/24.
Remaining part = (1 - 7/24) = 17/24.
Part filled by A in 1 min. = 1/40.
1/40 : 17/24 : : 1 : x
or x = (17/24 * 1 * 40) = 28.33 min.
= 28 min. 20 sec.
.'. The tank will be full in (5 + 28 min. 20 sec.) = 33 min. 20 sec