Question
Two inlet pipes 'A' and 'B' can fill an empty tank in 60
minutes and 90 minutes, respectively. Another outlet pipe 'C' can empty the tank in 180 minutes. If all the three pipes are opened together, then find the time taken by them to fill the tank.Solution
Let the total capacity of the tank be 180 litres (LCM of 60, 90, and 180).
Efficiency of 'A' = 180 ÷ 60 = 3 litres/minute
Efficiency of 'B' = 180 ÷ 90 = 2 litres/minute
Efficiency of 'C' = 180 ÷ 180 = -1 litre/minute
Required time = 180 ÷ (3 + 2 - 1) = 180 ÷ 4 = 45 minutes
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