A train crosses a post in 15 seconds and a platform 100 m long in 25 seconds. Its length is Answers:
A) 150 m  B) 300 m  C) 400 m  D) 180 m  E) 160 m

Rationale: explanation : assume x is the length of the train and v is the speed x / v = 15 = > v = x / 15 ( x + 100 ) / v = 25 = > v = ( x + 100 ) / 25 ie , x / 15 = ( x + 100 ) / 25 = > 5 x = 3 x + 300 = > x = 300 / 2 = 150 answer : option a
Answer: A