72. 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:

✅ The correct answer is option D.
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