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

    Question

    'C' can complete a work in 18 days whereas 'D' can do

    the same work in 30 days.They started working together but 'C' worked with 60% of his efficiency while 'D' worked with 50% of his efficiency. Find the total time taken by them to complete the work this way.
    A 25 days Correct Answer Incorrect Answer
    B 20 days Correct Answer Incorrect Answer
    C 18 days Correct Answer Incorrect Answer
    D 22 days Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ, Let the total work be 90 units (LCM of 18 and 30) So, efficiency of 'C' = (90/18) = 5 units/day And efficiency of 'D' = (90/30) = 3 units/day New efficiency of 'C' = 60% of 5 = (0.6) X 5 = 3 units/day New efficiency of 'D' = 50% of 3 = (0.5) X 3 = 1.5 units/day So, required time =(90/(3+1.5) = 90/4.5 = 20 days

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