I noticed you are learning Russian, too. Well, the Russian layout is different:
The reason being that about a thousand years ago it was as follows:
- 1 → use the singular
- 2 → use the dual
- 3,4 → use the plural
- anything else → treat as a noun and use the Genitive plural
Then the dual number was lost in most Slavic languages, the gaping holes patched up by whichever forms seemed "good enough".
Numbers combine with different forms of nouns (for historical reasons):
- один студент
- два студенти
- три студенти
- чотири студенти
- п'ять студентів
The form will depend on the last word of the numeral. In the "Nominative" case the noun will actually be in the Nominative for "one" (singular), "two"/"three"/"four" (plural).
As soon as you number ends in anything else you use the Genitive plural (as if your number were a noun):
- сім студентів
- одинадцять студентів
- вісімдесят студентів
- тридцять п'ять студентів
- сто студентів
It holds for 5 and up. The form depends on the last word of the numeral (e.g., один студент, п'ятьдесят один студент, шість студентів, тридцять чотири студенти).
But that's for the Nominative form (and matching Accusative form). For everything else, один-numerals use the singular noun and everything else uses the plural noun of whichever case you need in the sentence (e.g., не більше трьох доларів).
The primary reason for this madness is that Slavic languages used to have the dual number—and bigger numbers were like nouns. As the dual form disappeared, the holes were patched up by aligning 2 with 3 and 4.