A train with 72 km/h speed crosses a stationary pole in 35 seconds. How much time (in minutes) does it take to cross a 1.1 km long bridge?

1.5

Speed of train = 72 km/h

72 km/h = 72 × \(\frac{5}{18}\) m/sec = 20 m/sec

Distance = Speed × Time

= 20 ×  35 = 700 m

Now ,

Time taken by train to cross 1.1 km long bridge = 1100 + 700 = 1800 m

Time = \(\frac{Distance}{Speed}\)

= \(\frac{1800}{20 }\)

= 90 seconds

=  1.5 minutes