The time taken by a train $35\text{ m}$ long, running at $90\text{ km/hr}$, in crossing an electric pole is

Step 1: Convert speed from km/hr to m/s.
$$\text{Speed}=90\times \frac{5}{18}=5\times 5=25\text{ m/s}$$

Step 2: Calculate the time taken to cross the pole.
When crossing a stationary point object like an electric pole, the distance to be covered is equal to the length of the train itself.

$$\text{Distance}=35\text{ m}$$

$$\text{Time}=\frac{\text{Distance}}{\text{Speed}}=\frac{35}{25}=\frac{7}{5}=1.4\text{ seconds}$$

Hence, the time taken is $1.4\text{ seconds}$.