A 300 meter long train crosses a platform in 42 seconds while it crosses a signal pole in 18 seconds. What is the length of the platform? Choose the correct choice from the following choices:
A) 287m	B) 278m	C) 400m	D) 228m	E) 282m
Speed = [300 / 18] m/sec = 50/3 m/sec.   Let the length of the platform be x meters.   Then, x + 300 / 42   = 50/3   3(x + 300)   = 2100 è x   = 400m.   Answer:400m
<result>C</result>
A 300 meter long train crosses a platform in 42 seconds while it crosses a signal pole in 18 seconds. What is the length of the platform?