Learn German: Der Weg ist fünfundvierzig Kilometer lang. - The path is forty-five kilometers long.

In German, numbers from 21 to 99 are spoken and written backwards compared to English. You say the ones first, then und (and), and finally the tens. They are also written as one single, long word: fünf (5) + und + vierzig (40).

Why isn't there an "s" on the end of Kilometer if there are 45 of them?

In German, masculine and neuter nouns that are used as units of measurement (like Kilometer, Liter, or Euro) don't usually change their form when they follow a number. Also, the dictionary plural of der Kilometer is simply die Kilometer anyway!

Why doesn't the adjective lang have an ending here?

Adjectives in German only get extra endings (like -e or -er) when they sit directly in front of a noun, as in ein langer Weg (a long path). Because lang comes after the noun and the verb here, it stays in its basic, unchanged dictionary form.

Does Weg mean anything else besides "path"?

Yes! Der Weg is closely related to the English word "way" and is often used exactly like it. You will frequently see it used to mean "way", "route", or "road" when asking for directions.