A 400 meter long train crosses a platform in 45 seconds while it crosses a signal pole in 30 seconds. What is the length of the platform? Options:
A) 200
B) 400
C) 350
D) 1800
E) 45

Rationale: "speed = [ 400 / 30 ] m / sec = 40 / 3 m / sec . let the length of the platform be x meters . then , x + 400 / 45 = 40 / 3 3 ( x + 400 ) = 1800 è x = 200 m . answer : a"
Answer: A