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    Question

    Speed of a boat in still water to speed of boat in

    upstream is 5:4. If the boat can travel 360 km in downstream in 15 hours, then find the time taken by the boat to cover 15 km in still water.
    A 39 minutes Correct Answer Incorrect Answer
    B 45 minutes Correct Answer Incorrect Answer
    C 75 minutes Correct Answer Incorrect Answer
    D 48 minutes Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let speed of boat in still water and speed of boat in upstream be ‘5x’ km/h and ‘4x’ km/h, respectively. Speed of stream = 5x – 4x = x km/h Speed of boat in downstream = 5x + x = 6x km/h So, 6x = 360/15 Or, x = 4 Speed of boat in still water = 5 × 4 = 20 km/h Desired time = 15/20 x 60 = 45 minutes

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