A train 420 m long passes a pole in 20 seconds. What is the speed of the train?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 21 m/s
A pole has no length of its own, so to pass a pole the train covers only its own length: from the moment its front reaches the pole until its rear passes it.
Distance \(=420\) m (the length of the train)
Speed \(\displaystyle =\frac{420}{20}=21\) m/s