Question

A train passes an electric post in 20 s and a
bridge length 1 km in 120 s. The speed of the
train is:
(1) 24 km/h
(2) 36 km/h
(3) 72 km/h (4) 40 km/h.​

Answer 1

Answer:

(2)36km/h

Explanation:

The train passes a electric post in 20 seconds, that's mean the train passes his own length in 20 seconds.

Now, the train passes a 1km long bridge in 120 seconds. That's mean the train actually takes 100 seconds to pass the bridge(because it takes 20 seconds to pass his own distance).

Now we can say...

The train goes 1km in 100 seconds. And it goes 36 km in 1 hour.