Correct Answer - Option 2 : 310 m
Given:
Length of train = 140 m
Speed of train = 54 km/hr = 54 × (5/18) = 15 m/sec
Time required to cover the bridge = 30seconds
Concept Used:
Distance covered = Speed × Time
1 km/hr = 5/18 m/sec
Calculation:
Let, the length of the bridge is x m
To cross the bridge the train have to cross (140 + x) m
Accordingly,
140 + x = 15 × 30
⇒ x = 450 - 140
⇒ x = 310
∴ The length of the bridge is 310 m.
