Question
Pipe ‘A’ can fill a tank in 30 hours while pipe
‘B’ can empty it in 40 hours. They were operated on alternate hours starting with pipe ‘A’. Find the percentage of tank filled this way in 54 hours.Solution
Let the total capacity of tank be 120 units Efficiency of pipe ‘A’ = 120/30 = 4 units/hour Efficiency of pipe ‘B’ = 120/40 = 3 units/hour Tank filled in 2 hours = (4 – 3) = 1 units Therefore, tank filled in (2 × 27 = 54 hours) = 1 × 27 = 27 units Required percentage of tank filled = (27/120) × 100 = 22.5%
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