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    Question

    A train travelling at the speed of 72 km/hr crosses

    another train, having 60 meters less length and travelling in opposite direction at the speed of 54 km/hr in 6 seconds. If the longer train crosses a platform in 18 seconds, then the shorter train will cross the same platform in how many seconds?
    A 19 seconds Correct Answer Incorrect Answer
    B 20 seconds Correct Answer Incorrect Answer
    C 21 seconds Correct Answer Incorrect Answer
    D 22 seconds Correct Answer Incorrect Answer
    E 23 seconds Correct Answer Incorrect Answer

    Solution

    Speed of longer train = 72 ├Ч (5/18) = 20 m/s
    Speed of shorter train = 54 ├Ч (5/18) = 15 m/s

    Let length of longer and shorter trains be тАШLтАЩ meters and (L тАУ 60) metres, respectively.

    According to question,

    L + L тАУ 60 = (20 + 15) ├Ч 6 = 210

    2L тАУ 60 = 210

    L = 135 metres

    So, L тАУ 60 = 75 metres

    Let length of platform is тАШPтАЩ metres

    So, P + 135 = 20 ├Ч 18 = 360

    P = 360 тАУ 135 = 225 meters

    Desired time = (225 + 75)/15 = 300/15 = 20 seconds

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