A train speeds past a pole in 50 seconds and a platform 500 m long in 100 seconds. Its length is:	Select the correct option:
A) 550 m .
B) 300 m .
C) 600 m .
D) 400 m .
E) 500 m .

Rationale: "let the length of the train be x meters and its speed be y m / sec . they , x / y = 50 = > y = x / 50 x + 500 / 100 = x / 50 x = 500 m . answer : option e"
Answer: E