Question
Pipes ‘M’ and ‘N’ alone can fill a tank in 14
minutes and 21 minutes, respectively, while pipe ‘O’ can empty the same tank in 42 minutes. If all three pipes are opened together, then find the time taken to fill the tank.Solution
ATQ,
Let the capacity of the tank be 84 litres {LCM (14, 21, and 42)}
Efficiency of pipe ‘M’ = (84/14) = 6 litres/minute
Efficiency of pipe ‘N’ = (84/21) = 4 litres/minute
Efficiency of pipe ‘O’ = (84/42) = 2 litres/minute
Required time = {84 / (6 + 4 – 2)} = 12 minutes
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