A train 420 m long crosses a bridge 300 m long in 36 seconds. What is the speed of the train (in km/hr)?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 72
To cross a bridge completely, the train covers its own length plus the length of the bridge. A speed in m/s is changed to km/hr by multiplying by \(\frac{18}{5}\).
Distance \(=420+300=720\) m
Speed \(\displaystyle =\frac{720}{36}=20\) m/s
In km/hr: \(\displaystyle 20\times\frac{18}{5}=72\) km/hr