In what time will a railway train 50 m long moving at the rate of 36 kmph pass a telegraph post on its way?
Answers:
A) 5 sec  B) 4 sec  C) 3 sec  D) 6 sec  E) 1 sec

Rationale: "t = 50 / 36 * 18 / 5 = 5 sec answer : a"
Answer: A