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    Question

    ‘A’ alone can complete a work in 10 days. ‘B’

    alone can complete the same work in 20 days. If ‘A’ and ‘B’ work together for 3 days, then the remaining work can be completed by ‘A’ alone in how many days?
    A 4.5 days Correct Answer Incorrect Answer
    B 3.5 days Correct Answer Incorrect Answer
    C 5.5 days Correct Answer Incorrect Answer
    D 2.5 days Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let the total amount of work = 20 units {LCM of 10 and 20} Then, efficiency of ‘A’ = 20/10 = 2 units/day Efficiency of ‘B’ = 20/20 = 1 units/day Combined efficiency of ‘A’ and ‘B’ = 2 + 1 = 3 units/day Work completed by ‘A’ and ‘B’ together in 3 days = 3 × 3 = 9 units Remaining work = 20 – 9 = 11 units Time taken by ‘A’ alone to complete the remaining work = 11/2 = 5.5 days

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