Question

A train passes an electric pole in 8 seconds and a bridge of length 1 km in 108 seconds.The speed of the engine is?

Answer 1

Let the length of train be x

At electric pole,
Time taken = 8 s
speed of train = length of train/time
v = x/8

Now,
At bridge,
Time taken = 108 s
Distance = 1 km
But, total distance = 1 + x km
Speed = Total distance/Time
v = 1 + x/108



Now, in both the cases velocity/speed is same.

Therefore,

x/8 = 1+x/108
108x = 8 + 8x
100x = 8
x = 8/100 = 0.08 km


So, the length of train is 0.08 km

Now,
v = x/8
v = 0.08/8
v = 0.01 km/s
OR
v = 10m/s