# The length of the bridge, which a train 130 metres long and travelling at 45 km/hr

## The length of the bridge, which a train 130 metres long and travelling at 45 km/hr can cross in 30 seconds, is:

To solve this problem, we need to consider the speed and length of the train, as well as the time it takes to cross the bridge. Let's break it down step by step:

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

Speed in m/s = (45 km/hr) * (1000 m/km) / (3600 s/hr)

= 12.5 m/s

We are given that the train takes 30 seconds to cross the bridge. Let's denote the length of the bridge as "L" meters.

When the train is completely on the bridge, it travels a distance equal to its own length plus the length of the bridge, which is L + 130 meters.

We can calculate the distance traveled by the train using its speed and the time it takes to cross the bridge:

Distance = Speed * Time L + 130

= 12.5 * 30 L + 130 = 375

Solve for L:

L = 375 - 130 L

= 245 meters

Therefore, the length of the bridge is 245 meters.