Question

The length of the bridge, which a train 130 metres long and travelling at 45 km/hr can cross in 30 seconds, is:
(a) 200m
(b) 225m
(c) 245m
(d) 250m

Answer 1

Let the bridge be of length x m.
45 km/h=45*5/18 m/s=12.5 m/s.
Total Distance =(130+x) m.
Time =30 secs
Since S=D/T,
12.5=(130+x)/30
or,12.5*30=130+x
or,375=130+x
or,x=375-130
or,x=245
Therefore , length of bridge is 245 m.
Ans:(c)245 m

Answer 2

lets x be length of bridge
hence x+130 is total distance
x+130/30=45*5/18 ( we know that distance/time=velocity)
after solving this equation
you get x=245m