Two trains 230 m and 270 m long are running in opposite directions at speeds of 42 km/h and 48 km/h, respectively. They cross each other in:

Correct option is B

Given:

Length of the first train = 230 meters

Length of the second train = 270 meters

Speed of the first train = 42 km/h

Speed of the second train = 48 km/h

The trains are running in opposite directions.

Formula Used:

Relative speed = Speed of first train + Speed of second train

Time = $$\frac{\text{Total Distance}}{\text{Relative Speed}}$$​​

Solution:

Since the trains are running in opposite directions, their relative speed is:

Relative Speed = 42 km/h + 48 km/h = 90 km/h

The total distance is the sum of the lengths of both trains:

Total Distance = 230 m + 270 m = 500 m

Time = $$\frac{500 \, \text{m}}{90\times \frac {5}{18} \, \text{m/s}}= \frac{500 \times 18\, \text{m}}{90\times 5 \, \text{m/s}}= 20 \, \text{seconds}$$​

Thus, the two trains will take 20 seconds to cross each other.