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    Question

    Train 'M' takes 2 hours less than Train 'N' to travel a

    distance of 150 km. The speed of Train 'M' is 20 km/h more than that of Train 'N'. What is the time taken by Train 'N' to cover a distance of 360 km?
    A 24 hrs Correct Answer Incorrect Answer
    B 12 hrs Correct Answer Incorrect Answer
    C 20 hrs Correct Answer Incorrect Answer
    D 8 hrs Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let the speed of train 'N' be 'v' km/h. Speed of train 'M' = (v + 20) km/h ATQ, 150/v - 150/(v + 2) = 2 Or, 150(v +2) - 150v = 2v (v + 10) Or, v2 + 50v - 30v - 1,500 = 0 Or, v(v + 50) - 30(v + 50) = 0 Or, (v + 50) (v - 30) = 0 So, 'v' = 30 or 'v' = - 50 Speed cannot be negative. So, 'v' = 30 Therefore, time taken by train 'N' to cover 360 km = (360/30) = 12 hours 

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