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    Question

    A and B can do job in 10 days. B and C can do same job

    in 12 days. A, B and C together can do same job in 8 days. In how many days A and C together can complete the job?
    A 12 days Correct Answer Incorrect Answer
    B 15 days Correct Answer Incorrect Answer
    C 18 days Correct Answer Incorrect Answer
    D 20 days Correct Answer Incorrect Answer
    E 25 days Correct Answer Incorrect Answer

    Solution

    Total work = Number of days×1 day’s work (efficiency) Total work = LCM (10, 12, 8) = 120 unit 1 day’s work of (A+B) = 120/10 = 12 unit 1 day’s work of (B + C) = 120/12 = 10 unit 1 day’s work of (A + B + C) = 120/8 = 15 unit Now, 1 day’s work of A = 15 – 10 = 5 1 day’s work of C = 15 – 12 = 3 1 day’s work of A and C = 5 + 3 = 8 A and C together can complete the job in = 120/8 = 15 days

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