Pipe and Cistern 

In pipes and cisterns problems – we need to find out what portion of the tank each of the pipes fill or drain in unit time (say in a minute / hour / second) and then perform arithmetic operation on this value.

In this Study note we will discuss frequently asked  questions on pipe and cistern

Question 1.Two pipes can fill a cistern in 14 and 16 hours respectively. The pipes are opened simultaneously and it is found that due to leakage in the bottom of the cistern, it takes 32 minutes extra for the cistern to be filled up. When the cistern is full, in what time will the leak empty it ?

(a) 114 hr        (b) 112 hr        (c) 100 hr        (d) 80 hr          (e) 120 hr

 Solution:

Hence B is the correct option.

Question 2. A tank of 3600 cu m capacity is being filled with water. The delivery of the pump discharging the tank is 20% more than the delivery of the pump filling the same tank. As a result, twelve minutes more time is needed to fill the tank than to discharge it. Determine the rate of delivery of the pump filling the tank.

(a) 40 m³/min            (b) 50 m³/min            (c) 60 m³/min (d) 80 m³/min            (e) 58 m³/min

 Solution:

Hence B is the correct option.

Question 3. Pipe A can fill an empty tank in 30 hours while B can fill it in 45 hours. Pipe A and B are opened and closed alternatively i.e., first pipe A is opened, then B, again A and then B and so on for 1 hour each time without any time lapse. In how many hours the tank will be filled when it was empty, initially ?

(a) 36               (b) 54               (c) 48               (d) 60              (e) 34

 Solution:

Hence A is the correct option.

Question 4. Tap A fills a tank in 20 minutes while C empties it at 1/3rd the rate at which A fills it. At 12 : 00 noon, A and C are simultaneously started and when the tank is 50% full, tap A is turned off. At what time will the tank be empty?

(a) 12 : 35 pm    (b) 12 : 45 pm          (c) 12 : 30 pm       (d) 12 : 55 pm       (e) 1:00 pm

 Solution:

Hence B is the correct option.

Question 5. Two pipes A and B can fill a cistern in 15 hours and 10 hours respectively. A tap C can empty the full cistern in 30 hours. All the three taps were open for 2 hours, when it was remembered that the emptying tap had been left open. It was then closed. How much more time would it take for the cistern to be filled? (relative to the case where the emptying tap was closed before opening the filling pipes A and B)

(a) 30 min.      (b) 1.2 hours   (c) 24 min.      (d) 35 min.      (e) 45 min.

 Solution:

Hence C is the correct option.

Question 6. A cistern can be filled separately by two pipes P and Q in 45 minutes and 35 minutes respectively. A tap R at the bottom can empty the full cistern in 30 minutes. If the tap R is opened 7 minutes after the two pipes P and Q are opened then after what time from the opening of tap R the cistern becomes full?

(a) 40th minute          (b) 61st minute           (c) 37th minute           (d) None of these       (e) Can’t be determined

 Solution:

Hence C is the correct option.

Question 7. Three pipes A, B and C can fill a tank in 15 minutes, 20 minutes and 30 minutes respectively. All three pipes started to fill the tank at same time. The pipe C is closed 6 minutes before the tank is filled. In what time the tank will be full?

(a) 6 minutes      (b) 8 minutes          (c) 12 minutes      (d) 14 minutes       (e) 10 minutes

 Solution:

Hence B is the correct option.

Question 8. There is a hole in a water tank which can empty it in 8 hours. A pipe is opened which fills 6 litre water per minute in tank and now tank is emptied in 12 hours. What is the capacity of the tank?

(a) 8260 litre               (b) 8660 litre      (c) 8640 litre            (d) 8620 litres             (e) 8460 litres

 Solution:

Hence C is the correct option.