New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    An elephant can do a work as fast as two horses ‘A’

    and ‘B’ can do it by working together. If horse ‘A’ alone can complete the work in 9 hours and horse ‘B’ in 18 hours, then find the time taken by elephant to complete the work.
    A 18 hours Correct Answer Incorrect Answer
    B 4 hours Correct Answer Incorrect Answer
    C 12 hours Correct Answer Incorrect Answer
    D 16 hours Correct Answer Incorrect Answer
    E 6 hours Correct Answer Incorrect Answer

    Solution

    Let the total work = 18 units Efficiency of horse who can complete the work in 9 hours = 18/9 = 2 units/hour Efficiency of horse who can complete the work in 18 hours = 18/18 = 1 units/hour Therefore, time taken by both horses to complete the work together = 18/(2 + 1) = 6 hours Therefore, time taken by the elephant to complete the work = 6 hours

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