A 300 metre long train crosses a platform in 39 seconds while it crosses a signal pole in 18 seconds. What is the length of the platform?  Choose the correct choice from the following options.
A) 150 m
B) 200 m
C) 350 m
D) 400 m
E) None
Sol.   Speed = [300 / 18] m/sec = 50/3 m/sec.   Let the length of the platform be x metres.   Then, x + 300 / 39 = 50/3 ⇔ 3(x + 300) = 1950 ⇔ x = 350m.   Answer 350 m
<result>C</result>
A 300 metre long train crosses a platform in 39 seconds while it crosses a signal pole in 18 seconds. What is the length of the platform?