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 70 km upstream and 144 km downstream in 13 hours, then find the time taken by the boat to cover 180 km in still water.
    A 9.25 hours Correct Answer Incorrect Answer
    B 15.25 hours Correct Answer Incorrect Answer
    C 11.25 hours Correct Answer Incorrect Answer
    D 10.5 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. 70/7x + 144/9x = 13 10/x + 16/x = 13 26 = 13x x = 2 Speed of boat in still water = (7x + 9x)/2 = 8x = 8 × 2 = 16 km/h Desired time = 180/16 = 11.25 hours

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