"Seven secretaries work with the judge."
Translation:Oibríonn seachtar rúnaithe leis an mbreitheamh.
Wouldn’t the singular form of the noun be used with this number, viz seachtar rúnaí rather than seachtar rúnaithe?
I know that this is a really old question, and scilling doesn't need this answer at this point, but for anyone else encountering this exercise, and other examples using numbers of people, seachtar rúnaithe can be thought of as "a septet of secretaries", where the noun is in the genitive plural, whereas using the cardinal numbers with regular nouns, the nouns usually remains in the singular (so seacht gcathaoir, not seacht gcathaoireacha).
Ah, that makes sense, thank you. My Irish grammar book stated that the singular form of the noun should be used, but listed ban as an exception; it would have been clearer if it had stated that the genitive plural form should be used.
As I said on the other comment, not 100% sure. Just the only thing I can think of to get seachtar rúnaithe, seachtar fear, etc.
The plural form of the genitive case. For some nouns, it's the nominative singular, for others it's the nominative plural, and for some it's irregular. It all depends on which declension class the noun is in, and which plural ending it has.