Two trains of length 100 m and 200 m are 100 m apart. They start moving towards each other on parallel tracks, at speeds 54 kmph and 72 kmph. After how much time will the trains meet? Select the correct option:
A) 12 sec	B) 3 sec	C) 4 sec	D) 10 sec	E) 5 sec
They are moving in opposite directions, relative speed is equal to the sum of their speeds.   Relative speed = (45 + 72)*5/18= 
<gadget id="calculator">(45 + 72)*5/18</gadget>
<output>65/2 = around 32.5</output>
32.5 mps.   The time required= d/s = 100/32.5 = 3 sec.   ANSWER:3 sec
<result>B</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 54 kmph and 72 kmph. After how much time will the trains meet?