A train can cross a 1200-metre-long bridge completely in 16 seconds. It can cross a 1600-metre-long bridge completely in 20 seconds. What is the speed of the train?

360 km/h

Let length of train = l meter

According to question ,

\(\frac{1200 + l}{16}\) = \(\frac{1600 + l}{20}\) 

\(\frac{1200 + l}{4}\) = \(\frac{1600 + l}{5}\)

6000 + 5l = 6400 + 4l

l = 400 m

Length of train is 400 m .

Speed of  train = \(\frac{1200 +400}{16}\) = 100 m/sec

100 × \(\frac{18}{5}\) = 360 km/h