I think in the following sentence, alle should be replaced with jede:
Diese Busse fahren alle fünfzehn Minuten vom Hauptbahnhof ab.
It means that the buses leave every fifteen minutes, doesn't it? Are both correct? Do they mean exactly the same?
I think in the following sentence, alle should be replaced with jede:
Diese Busse fahren alle fünfzehn Minuten vom Hauptbahnhof ab.
It means that the buses leave every fifteen minutes, doesn't it? Are both correct? Do they mean exactly the same?
You use alle for "15 minutes" because "minutes" is plural. You would use jede for singulars, like jede halbe Stunde. You could not use them vice-versa.
I think it is something like a fixed term.
dwds says
alle bezeichnet den wiederkehrenden Wechsel; immer wieder nach
alle halbe(n), alle (drei) Stunden
mitteldeutsch aller
aller fünf Minuten, zwei Jahre, drei Schritt