Question
A pipe fills a tank in 20 hours, and another pipe empties it in 30 hours. If both pipes are opened together, how long will it take to fill the tank?
Solution
The rate of the filling pipe is 1/20. The rate of the emptying pipe is 1/30. Net rate = (1/20 - 1/30) = 1/60. Time taken = 60 hours. Correct Option: d) 60 hours
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