Given: Time to cross a man by the train in = 5 sec Length of a bridge = 300 m Time to cross a bridge by the train in = 20 sec Calculation: Let, the speed of the train = x m/s Length of the train = y m According to the question, ⇒ 5x = y ----(1) According to the question,
⇒ 20x = y + 300⇒ 20x = 5x + 300 [from (1)] ⇒ 15x = 300 ⇒ x = 20 ⇒ Speed of the train = 20 m/s ∴ Length of the train = (5 × 20) = 100 m