Two trains 200m and 300m long run at the speed of 70kmph and 50kmph 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) 10sec	B) 15sec	C) 18sec	D) 20sec	E) 22sec
Relative speed = 70+50= 
<gadget id="calculator">70+50</gadget>
<output>120</output>
120kmph * 5/18= 100/3 m/s   Distance covered in crossing each other = 200+300= 
<gadget id="calculator">200+300</gadget>
<output>500</output>
500m   Required time= 500*3/100= 
<gadget id="calculator">500*3/100</gadget>
<output>15</output>
15sec   Answer is 15sec
<result>B</result>
Two trains 200m and 300m long run at the speed of 70kmph and 50kmph in opposite directions in parallel tracks. The time which they take to cross each other is?