Question
Pipe ‘A’ and pipe ‘B’, together can fill 20% of
a tank in 5 hours while pipe ‘C’ takes 30 hours to empty it. Pipe ‘A’ and pipe ‘B’ were opened together. After 24 hours, pipe ‘C’ is also opened. Find the total time taken to fill the empty tank this way.Solution
Time taken by pipe ‘A’ and pipe ‘B’, together to fill the tank = 5/0.2 = 25 hours Let the total capacity of tank = 150 units Efficiency of pipe (A + B) = 150/25 = 6 units/hour Efficiency of pipe ‘C’ = 150/30 = 5 units/hour Tank filled by pipe (A + B) in 24 hours = 24 × 6 = 144 units Time taken by all three pipes to fill the remaining tank = (150 – 144)/(6 – 5) = 6 hours Total time taken = 24 + 6 = 30 hours
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