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    Question

    A boat can travel 10 km more in downstream than that in

    upstream, in 5 hours while the difference between the time taken by the same boat to travel 250 km and 126 km, in still water, is 4 hours. Find the approximate time taken by the boat to travel 233 km in downstream and 100 km in upstream.
    A 7 hours Correct Answer Incorrect Answer
    B 15 hours Correct Answer Incorrect Answer
    C 20 hours Correct Answer Incorrect Answer
    D 10 hours 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; (250/x) - (126/x) = 4 Or, (124/x) = 4 So, x = 31 Now, 5 x (31 + y) = 5 x (31 - y) + 10 Or, 155 + 5y = 155 - 5y + 10 Or,  10y = 10 So, y = 1 So, downstream speed of the boat = (31 + 1) = 32 km/hr And, upstream speed of the boat = (31 - 1) = 30 km/hr Required time taken = (233/32) + (100/30) ~ (7 + 3) ~ 10 hours

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