More math with trains

So it is basically saying the last car goes in and it takes 30 seconds for it to go out.

The train is 1km long so we need to subtract that from the size of the tunnel. So 3 km - 1 km = 2 km.
So it takes 30 seconds to travel 2 km. So to make that into a minute 30x2=60 and 2x2=4 so every minute the train travels 4 km.

Now we do 1x60=1 hour  4x60=240 per hour. So the train travels at 240km/hour