I live near a railroad track, so I get to watch the train go by every once in a while. Near my house, there is also a small bridge, which the train frequently goes over. Over the years of me watching the train, I did some math. The train is exactly 100 meters long and the bridge that was mentioned earlier is 400 meters long. If the train takes 30 seconds to travel across the bridge, how fast is the train traveling, assuming the train is moving at a constant speed. Write your answer in kilometers per hour.
