Question

a train passes through a tunnel 1.05 km long. the guard finds that he remains in a tunnel for 31.5 second find the speed of the train in km/h​

Answer 1

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Let the length of the train be x. Running at a speed of 60 kmph it passes through a 1.5 km long tunnel in 2 mins.

The distance covered by the engine is (x+1.5+x) in 2 minutes.

60 km covered in 60 min so in 2 min the engine would have covered 60*6/60 = 2 km.

Therefore (x+1.5+x) = 2 or

2x = 2–1.5 = 0.5, or

x = 0.25 km So the train is 250 m long.