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Discussion :: Problems on Trains

  1. A train travelling at 48 kmph completely crosses another train having half its length and travelling in opposite direction at 42 kmph, in 12 seconds. It also passes a railway platform in 45 seconds. The length of the platform is

    2. A.
    400 m
    B.
    450 m
    C.
    560 m
    D.
    600 m

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    Answer : Option A

    Explanation :

    Let the length of the first train be x metres.

    Then, the length of the second train is 1-sym-oparen-h1 x 1-sym-cparen-h1 metres.
    2
    Relative speed = (48 + 42) kmph = 1-sym-oparen-h1 90 x 5 1-sym-cparen-h1 m/sec = 25 m/sec.
    18
    Therefore [x + (x/2)] = 12 or 3x = 300     or     x = 200.
    25 2

    Therefore Length of first train = 200 m.

    Let the length of platform be y metres.

    Speed of the first train = 1-sym-oparen-h1 48 x 5 1-sym-cparen-h1 m/sec = 40 m/sec.
    18 3
    Therefore (200 + y) x 3 = 45
    40

    => 600 + 3y = 1800

    => y = 400 m.

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