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    Question

    A boat can travel 36 km upstream in 6 hours. The same

    boat can travel 63 km downstream in 3 hours. What is the speed of the boat in still water?
    A 9 km/h Correct Answer Incorrect Answer
    B 13.5 km/h Correct Answer Incorrect Answer
    C 15 km/h Correct Answer Incorrect Answer
    D 17.5 km/h Correct Answer Incorrect Answer

    Solution

    Upstream speed = 36 km / 6 hours = 6 km/h. Downstream speed = 63 km / 3 hours = 21 km/h. Let the speed of the boat in still water be B km/h and the speed of the stream be S km/h. Upstream speed = B − S = 6 km/h. Downstream speed = B + S = 21 km/h. Adding the two equations: 2B = 27 ⇒ B = 13.5 km/h. Ans. b

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