Two trains of length 200 m and 300 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? Choose the correct choice from the following options.
A) 87/7 sec	B) 20 sec	C) 80/9 sec	D) 80/5 sec	E) 20/7 sec
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 + 200 + 300)/30   = 600/30= 
<gadget id="calculator">600/30</gadget>
<output>20</output>
20 sec.   Answer: 20 sec
<result>B</result>
Two trains of length 200 m and 300 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?