Question

this question I have asked earlier and again I m m asking I have some doubt in it's process

Answer 1

Length of bridge=800m
Length of train=200m
Now
When the last part of train gets off the bridge then only it will be said that it crossed the bridge.
So, total distance travelled = 800+200 = 1000m = 1km
Speed of train = 50km/hr

Now,
Distance = speed *time
And, time = distance /speed
So,
Time = 1/50 hour
Or, time =
$\frac{1}{50} \times 3600 \: sec = 72sec = 1min12sec$

Hope this will be helping you ✌️