A 300 m long train crosses a platform in 54 sec while it crosses a signal pole in 18 sec. What is the length of the platform?	Choose the correct choice from the following answers.
A) 287	B) 350	C) 600	D) 277	E) 122

Rationale: "speed = 300 / 18 = 50 / 3 m / sec . let the length of the platform be x meters . then , ( x + 300 ) / 54 = 50 / 3 3 x + 900 = 2700 = > x = 600 m . answer : c"
Answer: C