Two trains 140 m and 200 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?
Select: A) 10.9 sec B) 10.1 sec C) 10.6 sec D) 10.8 sec E) 12.24 sec
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   = 140 + 200= 
<gadget id="calculator">140 + 200</gadget>
<output>340</output>
340 m.   Required time= 340 * 9/250= 
<gadget id="calculator">340 * 9/250</gadget>
<output>306/25 = around 12.24</output>
12.24 sec.   Answer:12.24 sec
<result>E</result>
Two trains 140 m and 200 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?