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    Question

    When travelling with the current, a man takes 3 hours

    to cover a certain distance that he would've covered in 9 hours while travelling against the current. If the current flows at 10 km/h, then find the distance (one way) covered by the boat.
    A 75 km Correct Answer Incorrect Answer
    B 90 km Correct Answer Incorrect Answer
    C 80 km Correct Answer Incorrect Answer
    D 60 km Correct Answer Incorrect Answer
    E 100 km Correct Answer Incorrect Answer

    Solution

    Let the speed of the boat in still water be 'x' km/hr Therefore, distance covered in upstream = 9 X (x - 10) km Also, distance covered in downstream = 3 X (x + 10) km According to the question, 9 X (x - 10) = 3 X (x + 10) Or, {(x + 10)/(x - 10)} = (9/3) = (3/1) Or, x + 10 = 3x - 30 Or, 2x = 40 => 'x' = 20 So, speed of the boat in still water = 20 km/h So, required distance = 3 X (20 + 10) = 90 km

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