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

    Question

    A work can be completed by ‘A’ and ‘B’, alone in

    12 days and 18 days, respectively. Find the number of days taken by ‘C’ to complete the same work alone if ‘A’, ‘B’ and ‘C’ together can complete the whole work in 4 days.
    A 2 days Correct Answer Incorrect Answer
    B 3 days Correct Answer Incorrect Answer
    C 7 days Correct Answer Incorrect Answer
    D 9 days Correct Answer Incorrect Answer

    Solution

    Let total work = 36 units (LCM of 12 and 18) Efficiency of ‘A’ = (36/12) = 3 units/day Efficiency of ‘B’ = (36/18) = 2 units/day Combined efficiency of ‘A’, ‘B’ and ‘C’ = (36/4) = 9 units/day Efficiency of ‘C’ = 9 – (3 + 2) = 4 units/day Required time taken = (36/4) = 9 days

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