Annabelle is taking the polar express all the way to the north pole! the polar express is 100 meters long and it takes 30 seconds to cross santa’s 400m ice bridge. what speed is the train going at?

The first thing you should know for this problem is the definition of speed.Speed is defined as the quotient between distance and time.
 v = d / t.
 Substituting the values, we have:
 v = (100 + 400) / (30) = 16.67 m / s
 answer
 the train going at 16.67 m / s