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    Question

    A boat can cover 80 km upstream and 200 km downstream in

    14 hours. Speed of the stream is how much less than the speed of the boat in still water if the boat can cover 64 km upstream and 160 km downstream in 10 hours?
    A 20 km/h Correct Answer Incorrect Answer
    B 16 km/h Correct Answer Incorrect Answer
    C 18 km/h Correct Answer Incorrect Answer
    D 15 km/h Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ, Let the upstream speed and downstream speed of the boat be x km/h and y km/h, respectively. So according to question: 80/x + 200/y = 14 ………………. (i) Also, 64/x + 160/y = 10 ……….. (ii) Solving (i) and (ii), we get x = 16 and y = 32 So, the upstream speed and downstream speed of the boat are 16 km/h and 32 km/h, respectively. Speed of the boat in still water = (16 + 32)/2 = 24 km/h Speed of the stream = (32 – 16)/2 = 8 km/h So, the desired difference = 24 – 8 = 16 km/h

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