Here are some sample sentences,
- He got first/1st class in that examination.
- He gave me two/2 books.
- He will be the first/1st to get there.
- My son is finishing his seventh/7th semester.
- The turkey weighed five/5 Kg.
Yes, I understand that we can have many examples like the above.
Do you think that you can give some general rules for these?