Question
Pipe βAβ can fill a tank in 20 hours while pipe
βBβ takes 30 hours to empty it. Pipe βAβ is opened alone when the tank was empty and after 11 hours pipe βBβ is also opened. In how much time will the tank get filled completely?Solution
Let the total capacity of the tank be 60 units Efficiency of pipe βAβ = 60/20 = 3 units/hour Efficiency of pipe βBβ = 60/30 = 2 units/hour Tank filled in 11 hours = 11 Γ 3 = 33 units Therefore, required time taken to fill the remaining tank = (60 β 33)/(3 β 2) = 27 hours Therefore, total time taken = 11 + 27 = 38 hours
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