Question

    In a fixed time, a boy swims thrice the distance along

    the current that he swims against the current. If the speed of the current is 9 km/hr, the speed of the boy in still water is
    A 10 km/hr Correct Answer Incorrect Answer
    B 14 km/hr Correct Answer Incorrect Answer
    C 12 km/hr Correct Answer Incorrect Answer
    D 8 km/hr Correct Answer Incorrect Answer
    E 18 km/hr Correct Answer Incorrect Answer

    Solution

    Let the rate of swimming in still water be x km/hr Rate down-stream = (x + 9) km/hr Rate up-stream = (x – 9) km/hr According to the question, (x + 9) t = 3 (x – 9) × t x + 9 = 3x – 27 x = 18 km/hr

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