Student: A 400 meter long train crosses a man standing on the platform in 10 sec. What is the speed of the train?
Options:
(A) 144
(B) 108
(C) 278
(D) 126
(E) 112.
Another student: Let's say, hmmm...

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
S = 400/10 * 18/5 = 144 kmph Final answer: (A).