Two trains 200m and 250m long run at the speed of 72kmph and 18kmph in opposite directions in parallel tracks. The time which they take to cross each other is?	Choose the correct choice from the following answers:
A) 5.6sec B) 8.9sec C) 10.8sec D) 12.6sec E) 18 sec
Relative speed = 72+18= 
<gadget id="calculator">72+18</gadget>
<output>90</output>
90 kmph * 5/18= 25 m/s   Distance covered in crossing each other = 200+250= 
<gadget id="calculator">200+250</gadget>
<output>450</output>
450m   Required time= 450*1/25= 
<gadget id="calculator">450*1/25</gadget>
<output>18</output>
18 sec   Answer is 18 sec
<result>E</result>
Two trains 200m and 250m long run at the speed of 72kmph and 18kmph in opposite directions in parallel tracks. The time which they take to cross each other is?