Two trains 200m and 250m long run at the speed of 72kmph and 18kmph in opposite directions in parallel tracks. The time which they take to cross each other is?	Pick one.
A) 5.6 sec  B) 8.9 sec  C) 10.8 sec  D) 12.6 sec  E) 18 sec

Rationale: "relative speed = 72 + 18 = 90 kmph * 5 / 18 = 25 m / s distance covered in crossing each other = 200 + 250 = 450 m required time = 450 * 1 / 25 = 18 sec answer is e"
Answer: E