Question

    A boat can travel 20 km more in downstream than that in

    upstream, in 10 hours while the difference between the time taken by the same boat to travel 210 km and 126 km, in still water, is 4 hours. Find the approximate time taken by the boat to travel 220 km in downstream and 183 km in upstream.
    A 10 hours Correct Answer Incorrect Answer
    B 19 hours Correct Answer Incorrect Answer
    C 12 hours Correct Answer Incorrect Answer
    D 15 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; (210/x) - (126/x) = 4 Or, (84/x) = 4 So, x = 21 Now, 10 x (21 + y) = 10 x (21 - y) + 20 Or, 210 + 10y = 210 - 10y + 20 Or, 20y = 20 So, y = 1 So, downstream speed of the boat = (21 + 1) = 22 km/hr And, upstream speed of the boat = (21 - 1) = 20 km/hr Required time taken = (220/22) + (183/20) ~ (10 + 9) ~ 19 hours

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