A cistern has two pipes one can fill it with water in 16 hours and other can empty it in 10 hours. In how many hours will the cistern be emptied if both the pipes are opened together when 3/5th of the cistern is already filled with water?

If both pipes are open, then total units per hour empty the tank (A-B) = 5-8 = -3 units According to question, Tank has 3/5 of its total capacity in the beginning 3/5 × 80= 48 units Time taken to empty the tank = 48/(-3) = 16 hours.

- In what time would a Cistern be filled by three pipes whose diameter are 2cm, 8/3cm and 4cm running together, where the largest pipe alone fill it in 183 minutes. The amount of water flowing in by each pipe being directly proportional to the square of diameter?
- Pipe ‘A’ takes 10 minutes to fill a tank. Pipe ‘B’ takes 20 minutes to empty the same tank. If pipe ‘B’ is opened 5 minutes after pipe ‘A’, then find the total time taken to fill the tank in this manner.
- Pipe ‘A’ can fill a tank in 25 hours while pipe ‘B’ can empty it in 30 hours. They were operated on alternate hours starting with pipe ‘A’. Find the percentage of tank filled this way in 60 hours.
- Two pipes A and B can fill a tank in 12 min., and 16 min, respectively. If both the pipes are opened simultaneously, after how much time A should be closed so that the tank is full in 12 minutes?
- Two inlet pipes M and N alone can fill a tank in 15 hours and 18 hours respectively and an outlet pipe P alone can empty the whole tank in 10 hours. First pipe M is opened for 6 hours, then pipe P is opened for 4 hours and rest of the tank is filled by pipe N. In what time will the tank be filled completely?
- Two pipes A and B can fill a cistern in `27 1/2` minutes and 35 minutes respectively. Both pipes are opened. The cistern will be filled in just 25 minutes, if the pipe B is turned off after:
- Pipe ‘A’ takes 15 minutes to fill a tank. Pipe ‘B’ takes 25 minutes to empty the same tank. If pipe ‘B’ is opened 11 minutes after pipe ‘A’, then find the total time taken to fill the tank in this manner.
- In what time would a cistern be filled by three pipes whose diameter are 2cm, 2*2/3cm, 4cm running together, when the largest pipe alone fill the cistern in 122 minutes the amount of water flowing in by each pipe being proportional to the square of diameter?
- Tap ‘A’ and tap ‘B’ can fill a tank in 42 hours and 30 hours, respectively. If both taps are opened together, then find the time after which tap ‘A’ must be closed so the whole tank can be filled in 20 hours.
- Pipe ‘A’ can fill a 120-litre tank in 24 hours. If pipe ‘A’ is 25% more efficient than pipe ‘C’ whereas pipe ‘B’ is 50% more efficient than pipe ‘C’, then find the time (in minutes) taken by all the given three pipes to fill the same tank together.

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