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Pipe A can fill a tank in 12 hours and Pipe B can fill the tank in 18 hours. If both the pipes are opened on alternate hours and if pipe B is opened first, then in how much time (in hours) the tank will be full?

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Pipe A can fill a tank in 12 hours and Pipe B can fill the tank in 18 hours. If both the pipes are opened on alternate hours and if pipe B is opened first, then in how much time (in hours) the tank will be full?


1). 14.5
2). 14
3). 15.5
4). 15


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Answered by on | Votes 0 |

1-hour Efficiency of pipe A: 1/12

1-hour Efficiency of pipe B: 1/18

If both opened together, work done in 2 hours: 1/18 + 1/12 = 5/36

After 14 hours, work done = 5 × 7/36 = 35/36.

Work left = 1 – 35/36 = 1/36. This work will be done by pipe B in h hours.

⇒ h/18 = 1/36

⇒ h = 1/2Therefore, total time = 14.5 hours

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