What ph516503 said -- or how about 'here are the twenty ducks I promised you'? Or 'where are the twenty ducks I left here yesterday?'? Or any number of cases like that? If you have an issue with the lack of usage opportunities, it seems to me your problem is with the 'twenty ducks' part, not with the 'the' part. The 'the' is necessary because it's written as 'les vignt canards', and you would translate that into English with a 'the'.
As far as my understanding goes they are very similar. I've sometimes heard regional accents pronounce (20) VINGT without the T or they make it barely audible. Although vingt-huit pronounced as "vin-huit" sounds strange to my ear. (Il y a une liaison obligatoire). I've noticed the Quebec French pronunciation of VINGT (20) can be quite distinguishable from VIN (wine).
Actually, you wouldn't believe the range of pet names that people use every day. Often the literal translation would leave you in shock, but they are used as terms of endearment. And, no, they are not considered to be derogatory or sexist. I'll let you discover them for yourself.
English speakers don't often use the article "the" as used here. I live on a farm and can't remember the last time I used "the" with twenty of any animal here. With all of these comments, please, duolingo, "Stop the clutter" of demanding the articles. It feels so weird to translate YOUR way. "The twenty ducks" is far less common than "Twenty ducks." Why can't we translate French into real English? I'm getting the opinion that duolingo is ignoring reasonable translations as well as these discussions. From now on, I'm going to skip my sensible English which I've acquired for 68 years and force myself to use French grammar in my English translations; or, I might just stop using this program. You could, you know, expand the sentence. Try "No, the twenty ducks over there." You can tell when English-speaking people are getting frustrated by the number of comments in the discussions (what duolingo calls "clutter"). English speakers do not need "the" to indicate number. We have a sounding S at the end of ducks.
I think the "report a problem" options should include "the English translation makes absolutely no sense!" Where on earth would this sentence be used? I know we're just using computer generated combinations of what we're meant to be learning but it's so frustrating when you're trying to re-learn French so you can have decent conversations with French people, and you get phrases like this. This is like the old Eddie Izzard joke when he says the only French he could remember from school is "le singe est dans l'arbre" and he's never yet been able to use it!