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    Question

    ‘A’ alone can do some work in 20 days. ‘B’ and

    ‘C’ together can do the same work in 15 days. If ‘B’ is half as efficient as ‘A’, then find the time taken by ‘C’ to complete the work alone.
    A 20 days Correct Answer Incorrect Answer
    B 22 days Correct Answer Incorrect Answer
    C 24 days Correct Answer Incorrect Answer
    D 21 days Correct Answer Incorrect Answer

    Solution

    Let the total work be 60 units. {LCM (20 and 15)} So, efficiency of ‘A’ = (60/20) = 3 units/day So, efficiency of ‘B’ = (3 x 0.5) = 1.5 unit/day Efficiency of ‘B’ and ‘C’ together = (60/15) = 4 units/day So, efficiency of ‘C’ = 4 – 1.5 = 2.5 units/day So, time taken by ‘C’ to finish the work alone = (60/2.5) = 24 days

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