Two pipes A and B can fill a tank in 20 and 30 minutes respectively. If both the pipes are used together, then how long will it take to fill the tank (M.A.T. 2003)

A cistern can be filled by a tap in 4 hours while it can be emptied by another tap in 9 hours. If both the taps are opened simultaneously, then after how much time will the cistern get filled (Hotel Management, 1997)

A tap can fill a tank in 6 hours. After half the tank is filled, three more similar taps are opened. What is the total time taken to fill the tank completely (S.S.C. 2003)

Answer:

A) 3 hrs 15min

B) 3 hrs 45 min

C) 4 hrs

D) 4 hrs 15 min

Explanation:

Time taken by one tap to fill half the tank = 3 hrs.

A water tank is two-fifth full. Pipe A can fill a tank in 10 minutes and pipe B can empty it in 6 minutes. If both the pipes are open, how long will it take to empty or fill the tank completely (Bank P.O. 1998)

Answer:

A) 6 min. to empty

B) 6 min. to fill

C) 9 min. to empty

D) None of these

Explanation:

Clearly, pipe B is faster than pipe A and so, the tank will be emptied

Pipe A can fill a tank in 5 hours, pipe B in 10 hours and pipe C in 30 hours. If all the pipes are open, in how many hours will the tank be filled (C.B.I. 1997)

Answer:

A) 2

B) 2.5

C) 3

D) 3.5

Explanation:

∴ All the three pipes together will fill the tank in 3 hours