Two trains of equal length are running on parallel lines in the same direction at 50 km/hr and 60 km/hr. The faster train passes the slower train in 72 seconds. The length of each train is:

Question: Two trains of equal length are running on parallel lines in the same direction at 50 km/hr and 60 km/hr. The faster train passes the slower train in 72 seconds. The length of each train is:

Solution:
Let the length of each train be x metres.
Then, distance covered = 2x metres.

Relative speed = (60 - 50) km/hr
= 10 km/hr
= (10× 1000)/3600 m/s
= 25/9 m/s

Now,
2x/72 = 25/9
⇒ 18x = 1800
∴ x = 100