A train crosses two bridges of 400 m and 160 m in 110 sec and 60 sec respectively. The length of the train is:

Let the length of the train be x m.
The train passes a bridge of length 400 m in 110 sec.
Speed of the train = (x + 400)/110...........(1)
The train passes another bridge of length 160 m in 60 sec.
Speed of the train = (x + 160)/60..............(2)

Equating equation (1) and (2),
⇒ (x + 400)/110 = (x + 160)/60
⇒ (x + 400) × 60 = (x + 160) × 110
⇒ (60x + 24000) = (110x + 17600)
⇒ 110x – 60x = 24000 – 17600
⇒ 50x = 6400
⇒ x = 6400/50
⇒ x = 128 m