Question

    A boat goes 18 km an hour in still water, but takes

    thrice time as much time in going the same distance against the current. The speed of the current (in km/hour) is :
    A 6 km/hr Correct Answer Incorrect Answer
    B 8 km/hr Correct Answer Incorrect Answer
    C 3 km/hr Correct Answer Incorrect Answer
    D 4 km/hr Correct Answer Incorrect Answer
    E 12 km/hr Correct Answer Incorrect Answer

    Solution

    Let the speed of the current be x kmph. According to the question, 18/(18 – x) = 3 ⇒ 54 – 3x = 18 ⇒ 3x = 54 – 18 ⇒ x = 36/3 = 12 km/hr

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