Two trains, 80 metres and 120 metres long, are running at the speed of 25 km/hr and 35 km/hr respectively in the same direction on parallel tracks. How many seconds will they takes to pass each other ?



[ A ]    48
[ B ]    64
[ C ]    70
[ D ]    72 right
Answer : Option D
Explanation :
ATQ,
Distance to be covered = 80+ 120 = 200m
Relative speed = (35 – 25) ×$5\over18$ = $25\over9$m/s
So, time required to cross each other = 200 × $29\over25$= 72 seconds

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