"These girls are famous."
Weren't japanese nouns lacking a specific gender/number ? As in 女の子 could mean one or many girls, in which case -たち could be discarded and it would still be a gramatically correct translation.
The tachi makes it explicitly plural when using pronouns. Watashi = I Watashi tachi = we
For nouns, they can be single or plural, but pronouns for people work a bit differently.
Yes, we know, but we are not dealing with a pronoun here, but a noun: 女の子
What confuses us noobs is that we didn't expect to have たち attached to a noun, but here we have: 女の子たち
Just using 女の子 is flagged incorrect by Duo (この女の子は有名です is wrong according to Duo).
What's up with that?
Hoping someone could shed light on this.
Maybe it's just to be crystal clear that you're talking about "these girls" and not "this girl".
It marked こちらの女の子たちは有名です as wrong though im pretty sure こちらの is just more polite than この.