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    Question

    A boat goes 9 km an hour in still water, but takes twice

    as much time in going the same distance against the current. The speed of the current (in km/hour) is :
    A 2.5 km/hr Correct Answer Incorrect Answer
    B 3.5 km/hr Correct Answer Incorrect Answer
    C 4.5 km/hr Correct Answer Incorrect Answer
    D 6 km/hr Correct Answer Incorrect Answer
    E 8 km/hr Correct Answer Incorrect Answer

    Solution

    Let the speed of the current be x kmph. According to the question, 9/(9 – x) = 2 ⇒ 18 – 2x = 9 ⇒ 2x = 18 – 9 ⇒ x = 9/2 = 4.5 km/hr

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