Explanation

Convert the speed of the train from km/hr to m/s:

45 km/hr = 45 × 1000 m / 3600 s = 12.5 m/s

The train crosses the bridge in 30 seconds, so the total distance covered is the length of the train plus the length of the bridge. Let's call the length of the bridge "x". Then, the total distance = 130 m (train length) + x.

Since the train crosses the bridge in 30 seconds, we can use the formula:

Distance = Speed × Time

Substitute the values:

130 m + x = 12.5 m/s × 30 s

Simplify the equation:

130 m + x = 375 m

Subtract 130 m from both sides:

x = 245 m

So, the length of the bridge is 245 m.