Two trains 180m and 360m long run at the speed of 60kmph and 30kmph in opposite directions in parallel tracks. The time which they take to cross each other is?	Options.
A) 21.6sec
B) 8.9sec
C) 10.8sec
D) 12.6sec
E) 15sec
Relative speed = 60+30= 
<gadget id="calculator">60+30</gadget>
<output>90</output>
90kmph * 5/18= 25 m/s   Distance covered in crossing each other = 180+360= 
<gadget id="calculator">180+360</gadget>
<output>540</output>
540m   Required time= 540*1/25= 
<gadget id="calculator">540*1/25</gadget>
<output>108/5 = around 21.6</output>
21.6 sec   21.6secnswer is 21.6sec
<result>A</result>
Two trains 180m and 360m long run at the speed of 60kmph and 30kmph in opposite directions in parallel tracks. The time which they take to cross each other is?