A train passes a 200 m long platform in 40 seconds and a man standing on the platform in 25 seconds. The speed of the train (km/hr) is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 48 km/hr
To pass a man, a train covers only its own length; to pass a platform, it covers its length plus the platform’s. The extra 15 seconds are therefore the time taken to cover the 200 m platform.
Time for the platform alone \(=40-25=15\) s
Speed \(\displaystyle =\frac{200}{15}=\frac{40}{3}\) m/s
In km/hr: \(\displaystyle \frac{40}{3}\times\frac{18}{5}=48\) km/hr
Tip: To change m/s into km/hr, multiply by \(\frac{18}{5}\). Option (1), \(\frac{200}{15}\), is the speed in m/s with the wrong unit attached.