A cistern can be filled up in 4 h by an inlet A. An outlet B can empty the cistern in 8 h. If both A and B are opened simultaneously, then after how much time the cistern get filled?


A) 5 h

B) 7 h

C) 8 h

D) 6 h

Correct Answer:
C) 8 h

Description for Correct answer:
Part filled by A in 1 h = \( \Large \frac{1}{4} \)

Part emptied by B in 1 h = \( \Large \frac{1}{8} \)

Part filled by(A + B) in 1 h

= \( \Large \frac{1}{4}+ \left(-\frac{1}{8}\right)=\frac{1}{4}-\frac{1}{8}=\frac{2-1}{8}=\frac{1}{8} \)

Therefore, Required time to fill the cistern = 8 h

Note \( \Large \frac{-1}{8} \) has been taken because it empties the tank.

Part of solved Pipes and Cisterns questions and answers : >> Aptitude >> Pipes and Cisterns








Comments

No comments available




Similar Questions
1). A pipe can fill a tank in 20 h. Due to a leak in the bottom, it is filled in 40 h. If the tank is full, how much time will the leak take to empty it?
A). 40 h
B). 30 h
C). 50 h
D). 30 h
-- View Answer
2). A pipe can fill a tank in 10 h, while an another pipe can empty it in 6 h. Find the time taken to empty the tank, when both the pipes are opened up simultaneously.
A). 11 h
B). 15 h
C). 18 h
D). 16 h
-- View Answer
3). Three taps are fitted in a cistern. The empty cistern is filled by the first and the second taps in 3 and 4 h, respectively. The full cistern is emptied by the third tap in 5 h. If all three taps are opened simultaneously, the empty cistern will be filled up in
A). \( \Large 1\frac{14}{23} \)
B). \( \Large 2\frac{14}{23} \)
C). 2 h 40 min
D). 1 h 56 min
-- View Answer
4). Pipe A can fill a tank in 30 min, while pipe B can fill the same tank in 10 min and pipe C can empty the full tank in 40 min. If all the pipes are opened together, how much time will be needed to make the tank full?
A). \( \Large 9\frac{3}{13} \) h
B). \( \Large 9\frac{4}{13} \) h
C). \( \Large 9\frac{7}{13} \) h
D). \( \Large 9\frac{9}{13} \) h
-- View Answer
5). Pipes A and B can fill a tank in 5 and 6 h, respectively. Pipe C can fill it in 30 h. If all the three pipes are opened together, then in how much time the tank will be filled up?
A). \( \Large 3\frac{3}{14} \) h
B). \( \Large 2\frac{1}{2} \) h
C). \( \Large 3\frac{9}{14} \) h
D). \( \Large 2\frac{1}{14} \) h
-- View Answer


6). Through an inlet, a tank takes 8 h to get filled up. Due to a leak in the bottom, it takes 2 h more to get it filled completely. If the tank is full, how much time will the leak take to empty it?
A). 16 h
B). 20 h
C). 32 h
D). 40 h
-- View Answer
7). A tap can fill an empty tank in 12 h and a leakage can empty the tank in 20 h. If tap and leakage both work together, then how long will it take to fill the tank?
A). 25 h
B). 40 h
C). 30 h
D). 35 h
-- View Answer
8). Three taps A, B and C together can fill an empty cistern in 10 min. The tap A alone can fill it in 30 min and the tap B alone can fill it in 40 min. How long will the tap C alone take to fill it?
A). 16 min
B). 24 min
C). 32 min
D). 40 min
-- View Answer
9). Two pipes P and Q can fill a cistern in 12 and 15 min, respectively. If both are opened together and at the end of 3 min, the first is closed. How much longer will the cistern take to fill?
A). \( \Large 8\frac{1}{4} \)
B). \( \Large 8\frac{3}{4} \)
C). 5 min
D). \( \Large 8\frac{1}{2} \)
-- View Answer
10). There are three pipes connected with a tank. The first pipe can fill \( \Large \frac{1}{2} \) part of the tank in 1 h, second pipe can fill \( \Large \frac{1}{3} \) part of the tank in 1 h. Third pipe is connected to empty the tank. After opening all the three pipes, \( \Large \frac{7}{12} \) part of the tank can be filled in 1 h, then how long will third pipe take to empty the full tank?
A). 3 h
B). 4 h
C). 5 h
D). 6 h
-- View Answer