Discussion :: Time and Work

Two trains 140 m and 160 m long run at the speed of 60 km/hr and 40 km/hr respectively in opposite directions on parallel tracks. The time (in seconds) which they take to cross each other, is:
Answer : Option D
Explanation :
Relative speed = (60 + 40) km/hr =  100 x  5  m/sec  =  250  m/sec.  
18  9 
Distance covered in crossing each other = (140 + 160) m = 300 m.
Required time =  300 x  9  sec  =  54  sec = 10.8 sec.  
250  5 
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