Two trains of length 150 m and 250 m are 100 m apart. They start moving towards each other on parallel tracks, at speeds 18 kmph and 36 kmph. In how much time will the trains cross each other?  Select the correct option:
A) 87/7 sec B) 80/7 sec C) 100/3 sec D) 80/5 sec E) 20/7 sec
Relative speed = (18 + 36)* 5/18 = 3 * 5= 
<gadget id="calculator">3 * 5</gadget>
<output>15</output>
15 mps.   The time required= d/s = (100 + 150 + 250)/15   = 500/15 = 100/3 sec.   Answer: 100/3 sec
<result>C</result>
Two trains of length 150 m and 250 m are 100 m apart. They start moving towards each other on parallel tracks, at speeds 18 kmph and 36 kmph. In how much time will the trains cross each other?