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 which they take to cross each other, is

A. 9.8 seconds

B. 10.8 seconds

C. 11.8 seconds

D. 12.8 seconds

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Correct Answer :

B. 10.8 seconds

Relative Speed = 60+40 = 100 kmph
= 100*(5/18) = 250/9 m/sec
Distance = 140+160 = 300 meters
Time = Distance/Speed

300 \times \frac{9}{250} = \frac{54}{5} = 10.8 s e c o n d s

So the time trains will take to cross each other will be 10.8 seconds