Question

A train travelling at 48 km/h completely crosses another train having half the length of first train and travelling in opposite direction at 42 km/h in 12 seconds. The train having speed 48 km/h also passes a railway platform in 45 seconds. What is the length of the platform?

• A. 600m
• B. 300m
• C. 400m
• D. 200m

Answer 1

The Correct Option is C

Let the length of the first train be \( L \). The relative speed of the two trains is \( 48 + 42 = 90 \, \text{km/h} \). 
Converting this to meters per second, we get \( 90 \times \frac{5}{18} = 25 \, \text{m/s} \). 
The total distance covered when the two trains cross each other is \( L + \frac{L}{2} = \frac{3L}{2} \). 

Since the time taken is 12 seconds, \( \frac{3L}{2} = 25 \times 12 \), so \( L = 200 \, \text{meters} \). 
The length of the platform is then \( \frac{200}{45} \times 1000 = 400 \, \text{meters} \).