Two trains of equal length are running on parallel lines in the same direction at speeds of 101 km/h and 29 km/h. The faster train passes the slower train in 21 seconds. The length of each train is:

Correct option is A

Given:

Speed of the faster train = 101 km/h

Speed of the slower train = 29 km/h

Time taken for the faster train to pass the slower train = 21 seconds

The length of both trains is equal.

Formula Used:

Distance = Speed × Time

Solution:

Relative speed = Speed of faster train - Speed of slower train

Relative speed = 101 - 29 = 72 km/h

Relative speed in m/s =$$\frac{72 \times 1000}{3600} = 20 \, \text{m/s}$$​

Distance covered = 2$$0 \times 21 = 420 \, \text{m}$$​

The distance covered is the sum of the lengths of the two trains, and since the trains are of equal length, each train's length is:

Length of each train =$$\frac{420}{2} = 210 \, \text{m}$$​