Correct Answer - Option 2 : 4 : 5
Given:
Length of train = 280 m, and length of bridge = 70 m
Concept:
When speed is constant, the ratio of time is equal to the ratio of distance
Calculation:
When train crosses an electric pole, then
The distance covered by train = 280 m
When train crosses a bridge, then
The distance covered by train = 280 + 70 = 350 m
Now,
The ratio of time taken by a train crosses an electric pole and a bridge
⇒ 280 : 350
⇒ 4 : 5
∴ The required ratio is 4 : 5.