Correct Answer - Option 2 : 720 meter
Given:
Speed of train = 72 km/h
Time taken to cross the platform = 48 sec
Concept:
Speed = distance/time
Calculation:
Let, the Length of the train = x meter
∴ Length of platform = 3x meter
Speed of train in m/s = 72 × (5/18) = 20 m/s
According to the question,
⇒ (x + 3x)/20 = 48
⇒ x + 3x = 960
⇒ 4x = 960
⇒ x = 240
∴ Length of platform = 3x = (3 × 240) = 720 meter