A $150m$ long train is moving with a uniform velocity of $45km/hr$. The time taken by the train to cross a bridge of length $850m$ is:

The correct option is A

80 s

Given, length of train $=150m,$ length of bridge $=850m,$ and velocity of train $=45kmph=45\times \frac{5}{18}m{s}^{-1}$

Total distance to be covered for crossing the bridge

$=$ length of train $+$ length of bridge

$=150+850=1000m$

$Time=\frac{\text{Distance}}{\text{velocity}}=\frac{1000}{45\times \frac{5}{18}}=80s$