A 400 m long train passes a railway platform in 20 seconds with speed 90 km/hr. What is the length of platform?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 100 m
To pass a platform completely, a train must cover its own length plus the length of the platform. The speed is turned into metres per second first (1 km/h \(=\frac{5}{18}\) m/s).
Speed \(\displaystyle =90\times\frac{5}{18}=25\) m/s
Distance covered in 20 s \(=25\times20=500\) m
Length of the platform \(=500-400=100\) m