Two trains of equal lengths are running on parallel lines in the same direction at the rate of 56 km/hr and 46 km/hr. The faster train passes the slower train in 36 seconds. What is the length of the trains ?

Question: Two trains of equal lengths are running on parallel lines in the same direction at the rate of 56 km/hr and 46 km/hr. The faster train passes the slower train in 36 seconds. What is the length of the trains ?

Solution:
Let the length of each train be x metres.
Then, distance covered = 2x metres
.Relative speed = (56 - 46)km/hr
= 10 km/hr.
= 10 (5/18) m/sec.
= 25/9 m/sec.

Now
2x/36 = 25/9
2x × 9 = 36 × 25
18x = 36 × 25
x = (36 × 25)/18
x = 50