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    Question

    The ratio of the speed of boat in upstream to speed of

    boat in downstream is 7:9. If the boat can cover a total of 91 km upstream and 126 km downstream in 9 hours, then find the time taken by the boat to cover 180 km in still water.
    A 7.5 hours Correct Answer Incorrect Answer
    B 5.5 hours Correct Answer Incorrect Answer
    C 3.5 hours Correct Answer Incorrect Answer
    D 4.5 hours Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let speed of boat in upstream and downstream be ‘7x’ km/h and ‘9x’ km/h respectively. 91/7x + 126/9x = 9 13/x + 14/x = 9 27 = 9x x = 3 Speed of boat in still water = (7x + 9x)/2 = 8x = 8 × 3 = 24 km/h Desired time = 180/24 = 7.5 hours

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