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    Question

    A boat can travel 18 km more in downstream than that in

    upstream, in 9 hours while the difference between the time taken by the same boat to travel 200 km and 100 km, in still water, is 5 hours. Find the approximate time taken by the boat to travel 250 km in downstream and 200 km in upstream.
    A 12 hours Correct Answer Incorrect Answer
    B 32 hours Correct Answer Incorrect Answer
    C 42 hours Correct Answer Incorrect Answer
    D 22 hours Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let the speed of boat in still water and speed of stream be 'x' km/hr and 'y' km/hr, respectively. According to question; (200/x) - (100/x) = 5 Or, (100/x) = 5 So, x = 20 Now, 9 x (20 + y) = 9 x (20 - y) + 18 Or, 180 + 9y = 180 - 9y + 18 Or, 18y = 18 So, y = 1 So, downstream speed of the boat = (20 + 1) = 21 km/hr And, upstream speed of the boat = (20 - 1) = 19 km/hr Required time taken = (250/21) + (250/19) ~ (12 + 10) ~ 22 hours

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