A train speed past a pole in 15 seconds and a platform 100 m long in 25 seconds. Its length is ?



A train speed past a pole in 15 seconds and a platform 100 m long in 25 seconds. Its length is ?

A. 50 m

B. 150 m

C. 200 m

D. None of these

Answer : B. 150 m


Explanation :

    Let the length of the train be x metres and its speed by y m/sec.
    Then, x / y = 15
    => y = x / 15
    (x + 100) / 25 = x / 15
    => 15(x + 100) = 25x
    => 15x + 1500 = 25x
    => 1500 = 10x
    => x = 150 m.


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