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

45 x
5
m/sec
=

25
m/sec.

18
2

Time = 30 sec.
Let the length of bridge be x metres.

Then,
130 + x
=
25

30
2

2(130 + x) = 750
x = 245 m.

Video Explanation: https://youtu.be/M_d8WufJWKc