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    Question

    An elephant can do a work as fast as two horses

    lsquo;Arsquo; and lsquo;Brsquo; can do it by working together. If horse lsquo;Arsquo; alone can complete the work in 30 hours and horse lsquo;Brsquo; in 45 hours, then find the time taken by elephant to complete the work.
    A 12 hours Correct Answer Incorrect Answer
    B 10 hours Correct Answer Incorrect Answer
    C 18 hours Correct Answer Incorrect Answer
    D 24 hours Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let the total work = 90 units Efficiency of horse who can complete the work in 30 hours = 90/30 = 3 units/hour Efficiency of horse who can complete the work in 45 hours = 90/45 = 2 units/hour Therefore, time taken by both horses to complete the work together = 90/(3 + 2) = 18 hours Therefore, time taken by the elephant to complete the work = 18 hours

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