New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    Pipes ‘A’ and ‘B’ can fill a tank in 9 hours and

    12 hours, respectively. If pipe ‘C’ is opened along with pipes ‘A’ and ‘B’, then the tank gets filled in 9 hours. Find the time taken by pipe ‘C’ to empty (3/5) the part of the same tank.
    A 7.2hours Correct Answer Incorrect Answer
    B 14.6hours Correct Answer Incorrect Answer
    C 3.6hours Correct Answer Incorrect Answer
    D 9.6hours Correct Answer Incorrect Answer

    Solution

    Let the capacity of the tank = 36 liters (lcm of 9 and 12) Efficiency of pipe ‘A’ = (36/9) = 4 liters/hour Efficiency of pipe ‘B’ = (36/12) = 3 liters/hour Efficiency of all the three pipes together = (36/9) = 4 liters/hour Efficiency of pipe ‘C’ = 4 – (4 + 3) = (-3) liter/hour {Negative sign shows that pipe ‘C’ is an outlet pipe} Required time taken = {(3/5) × 36)}/3 = 7.2 hours

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