Question
Pipes βAβ and βBβ can fill a tank in 6 hours and
8 hours, respectively and pipe βCβ can empty the full tank in 12 hours. All three pipes are opened together, but after 2 hours pipe βBβ is closed while pipes βAβ and βCβ are opened until the tank is full. How many hours will the empty tank be filled this way?Solution
Let the capacity of the tank be (L.C.M of 6, 8, and 12) = 24 units Efficiency of pipe βAβ = 24/6 = 4 units/hour Efficiency of βBβ = 24/8 = 3 units/hour Efficiency of βCβ = 24/12 = 2 units/hour Effective efficiency of (A + B β C) = 4 + 3 β 2 = 5units/hour In 2 hours, part of the tank will be filled = 5 Γ 2= 10 units Remaining part = 24 -10 = 14 units time taken to fill the remaining part of the tank by A and C = 14/2=7 Total timing =2+7 =9hours
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