A train completely crosses a bridge of length 80 m in 15 s. Find the length of the train if its speed is 72 km/h.

220 m

Speed of train = 72 km/h = 20 m/sec

Distance = Speed × Time

Total Distance covered by it in 15 seconds  = 20 × 15 = 300 m

Total distance covered = Length of train + Length of platfor

So , Length of bridge = 300 - 80 = 220 m