Two trains 300 m and 450 m long run at the speed of 60 km/hr and 40 km/hr respectively in opposite directions on parallel tracks. The time which they take to cross each other is?
Choose the correct answer:  A) 10.6  B) 27  C) 10.4  D) 10.8  E) 10.1
Relative speed = 60 + 40= 
<gadget id="calculator">60 + 40</gadget>
<output>100</output>
100 km/hr.= 100 * 5/18 = 250/9 m/sec.   Distance covered in crossing each other = 300 + 450= 
<gadget id="calculator">300 + 450</gadget>
<output>750</output>
750 m.   Required time= 700 * 9/250 = 27 sec.   Answer: 27
<result>B</result>
Two trains 300 m and 450 m long run at the speed of 60 km/hr and 40 km/hr respectively in opposite directions on parallel tracks. The time which they take to cross each other is?