Question

Two pipes can fill a tank in 3 hours and 6 hours respectively. A third pipe can empty it in 9 hours.
If the tank is empty and all the pipes are opened together, in how many hours will the tank be
full.
Answer should be in fraction .....
Be fast i need answer argently​

Answer 1

Answer:

2 whole 4/7 hours

Explanation:

One pipe can fill tank in 3 hours. This means 1/3 tank will be filled by the first pipe in 1 hour. Second pipe can fill the tank in 6 hours. This means 1/6 tank will be filled by the second pipe in 1 hour. Third pipe empties the tank in 9 hours. This means 1/9 tank will be emptied by the third pipe in 1 hour.

Part of tank filled in 1 hour = 1/3 + 1/6 - 1/9 = (6+3-2) / 18 = 7/18

Hence, the tank would be full in 18/7 hours or 2 whole 4/7 hours.