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    Question

    ‘A’ alone can complete a work in 12 days. ‘B’ alone can complete the same work in 24 days. If ‘A’ and ‘B’ work together for 4 days, then the remaining work can be completed by ‘A’ alone in how many days?

    A 5 days Correct Answer Incorrect Answer
    B 7 days Correct Answer Incorrect Answer
    C 6 days Correct Answer Incorrect Answer
    D 8 days Correct Answer Incorrect Answer

    Solution

    Let the total amount of work = 24 units {LCM of 12 and 24} Then, efficiency of ‘A’ = 24/12 = 2 units/day Efficiency of ‘B’ = 24/24 = 1 units/day Combined efficiency of ‘A’ and ‘B’ = 2 + 1 = 3 units/day Work completed by ‘A’ and ‘B’ together in 4 days = 3 × 4 = 12 units Remaining work = 24 – 12 = 12 units Time taken by ‘A’ alone to complete the remaining work = 12/2 = 6 days

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