Subject

    Quantitative Aptitude

    Topic

    Speed & Distance

    A train overtakes two persons who are walking in the same direction in which the train is going, at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively. The length of the train is:

    ক)
    45 m
    খ)
    50 m
    গ)
    54 m
    ঘ)
    72 m

    Explanation

    2 kmph = (2 x  (5/18) m/sec. = (5/9) m/sec. 4 kmph = (4 x  (5/18)) m/sec = 10/9 m/sec. Let the length of the train be x metres and its speed by y m/sec. Then,   (x)/(y-(5/9)) = 9 and (x)/(y-(10/9)) = 10. Therefore, 9y - 5 = x and 10(9y - 10) = 9x => 9y - x = 5 and 90y - 9x = 100. On solving, we get: x = 50. Therefore, Length of the train is 50 m.

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