Two trains of length 100 m and 200 m are 100 m apart. They start moving towards each other on parallel tracks, at speeds 36 kmph and 72 kmph. In how much time will the trains cross each other?
Answers:
A) 70/3 sec  B) 80/3 sec  C) 40/3 sec  D) 60/3 sec  E) 90/3 sec
C   Relative speed = (36 + 72)* 5/18 = 6 * 5= 
<gadget id="calculator">6 * 5</gadget>
<output>30</output>
30 mps.   The time required= d/s = (100 + 100 + 200)/35   = 400/30 = 40/3 sec.
<result>C</result>
Two trains of length 100 m and 200 m are 100 m apart. They start moving towards each other on parallel tracks, at speeds 36 kmph and 72 kmph. In how much time will the trains cross each other?