Two trains, one 160 m and the other 140 m long are running

Home » Aptitude » Speed, Time and Distance » Question

Two trains, one 160 m and the other 140 m long are running in opposite directions on parallel rails, the first at 77 km an hour and the other at 67 km an hour. How long will they take to cross each other?

1. 7 seconds
2. 7 1 seconds
  2
3. 6 seconds
4. 10 seconds

Correct Option: B

If two trains be moving in opposite directions at rate u and v kmph respectively, then their
relative speed = (u + v) kmph.
Further, if their length be x and y km. then time taken to cross

each other =	x + y	hours.
	u + v

Here,
Total length = 160 + 140 = 300m.
Relative speed = (77 + 67) kmph

= 144 kmph = 144 ×	5	m/s or 40 m/sec.
	18

∴ Time =	300	= 7	1	Seconds
	40		2

7	1	seconds
	2