Question

    The ratio of the speed of the boat in upstream to that

    of in downstream is 3:4, respectively. If the speed of the current is 5 km/h, then find the speed of the boat in still water.
    A 25 km/h Correct Answer Incorrect Answer
    B 30 km/h Correct Answer Incorrect Answer
    C 35 km/h Correct Answer Incorrect Answer
    D 30 km/h Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    According to the question: Let the speed of the boat in still water = x km/h Speed of the boat downstream = (x+5) km/h Speed of the boat upstream = (x−5) km/h According to the question, (x−5):(x+5)=3:4 4(x−5)=3(x+5) 4x−20=3x+15 4x−3x=15+20 x=35 km/h

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