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    Question

    ‘A’ alone can complete a work in 15 days. ‘B’ alone can complete the same work in 18 days. If ‘A’ and ‘B’ work together for 6 days, then the remaining work can be completed by ‘A’ alone in how many days?

    A 4.5 days Correct Answer Incorrect Answer
    B 5 days Correct Answer Incorrect Answer
    C 5.5 days Correct Answer Incorrect Answer
    D 4 days Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let the total amount of work = 90 units {LCM of 15 and 18} Then, efficiency of ‘A’ = 90/15 = 6 units/day Efficiency of ‘B’ = 90/18 = 5 units/day Combined efficiency of ‘A’ and ‘B’ = 6 + 5 = 11 units/day Work completed by ‘A’ and ‘B’ together in 6 days = 6 × 11 = 66 units Remaining work = 90 – 66 = 24 units Time taken by ‘A’ alone to complete the remaining work = 24/6 = 4 days

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