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?

A. 9 s
B. 6 s
C. 10 s
D. 10.8 s

Explanation:

Relative speed = (60 + 40) km/hr
=[ 100 x ( 5 / 18 ) ]m/sec
= ( 250 /9 ) m/sec.

Distance covered in crossing each other = (140 + 160) m
= 300 m.

Required time = [ 300 x ( 9/250 ) ] sec

= ( 54/ 5 )sec

= 10.8 sec.