Two trains of length 100 m and 200 m are 100 m apart. They start moving towards each other on parallel tracks, at speeds 18 kmph and 72 kmph. In how much time will the trains cross each other?
Options:
A) 8 B) 16 C) 11 D) 12 E) 21
Relative speed = (18 + 72)* 5/18= 
<gadget id="calculator">(18 + 72)* 5/18</gadget>
<output>25</output>
25 mps.   The time required= d/s = (100 + 100 + 200)/25   = 400/25= 
<gadget id="calculator">400/25</gadget>
<output>16</output>
16 sec.   Answer:16
<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 18 kmph and 72 kmph. In how much time will the trains cross each other?