A 300 m long train crosses a platform in 39 sec while it crosses a signal pole in 9 sec. What is the length of the platform?  Choose one:
A) 389 m
B) 350 m
C) 289 m
D) 799 m
E) 1000 m

Rationale: speed = 300 / 9 = 100 / 3 m / sec . let the length of the platform be x meters . then , ( x + 300 ) / 39 = 100 / 3 = > x = 1000 m . answer : e
Answer: E