A train crosses a platform 100 metres long in 60 seconds at a speed of 45 km per hour. The time taken by the train to cross an electric pole is?

Let the length of train = L metres
Speed of train = 45 x (5/18) = 25/2 m/sec.
Distance covered in crossing the platform = (L + 100) m
∴ (L + 100) x (2/25) = 60
⇒ 2L + 200 = 1500
⇒ L = 650.
Now, time taken to cross the pole = 650 x (2/25) = 52 sec.