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    Question

    The speed of a boat in still water and the speed of the

    stream are in the ratio 7:2. If the boat takes 12 hours to travel 240 km upstream, how long will it take the boat to travel 144 km downstream?
    A 2.5 hrs Correct Answer Incorrect Answer
    B 5 hrs Correct Answer Incorrect Answer
    C 3 hrs Correct Answer Incorrect Answer
    D 4 hrs Correct Answer Incorrect Answer
    E 6 hrs Correct Answer Incorrect Answer

    Solution

    Let speed of boat in still water and speed of stream be '7x' km/hr and '2x' km/hr, respectively. So, upstream speed of boat = 7x - 2x = '5x' km/hr ATQ, (240/5x) = 12 Or, 'x' = 4 So, downstream speed of the boat = 7x + 2x = 9x = 9 X 4 = 36 km/hr Therefore, required time = (144/36) = 4 hours

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