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

(b) 9.6

(c) 10

(d) 10.8

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.