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    Question

    Working alone, B can complete the work in 20 days. C is

    twice as efficient as B and A takes 2 days more than it takes C to complete the work. Working together, in how much time would they be able to complete 7 such works?
    A 28 days Correct Answer Incorrect Answer
    B 30 days Correct Answer Incorrect Answer
    C 32 days Correct Answer Incorrect Answer
    D 33 days Correct Answer Incorrect Answer
    E 36 days Correct Answer Incorrect Answer

    Solution

    Time taken by B to complete the work = 20 days Time taken by C to complete the work =20/2 = 10 days Time taken by A to complete the work alone = 10 + 2 = 12 days Work done by A, B and C together in 1 day. ⇒ (1/20+ 1/10 + 1/12) = (3 + 6 + 5)/60 = 14/60 this means if would take 30/7 days for A, B and C to complete the work together ∴ Time taken A, B and C to complete 7 works = 7 × 30/7 days = 30 days

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