"Mam dwoje oczu i dwoje uchu"
I didn't have time to write this in the lesson, so I guess I have to make a discussion post here. 1. Why the collective numbers? 2. Aren't nouns after collective numbers supposed to be in the genitive plural? 3. Why doesn't the timed practice stop when I try to read the sentence discussion? Because of this, I never have time to read about a sentence if I'm confused...
Firstly, it should be "Mam dwoje oczu i dwoje uszu". It troubles some natives too and actually isn't used in everyday conversations. It's kinda hard to explain it, but I'll try my luck. If there is any general grammar rule for it, I'm not aware of it. There simply are some words that need to be used with collective numbers in such sentences. It's the same with "Mam dwoje dzieci" (I have two kids). I guess those are our language exceptions that you have to memorize. The thing with cases is that you can't just say that there supposed to be anything after collective numbers, because in theory we decline it as a phrase. Here is a full declination of "dwoje oczu" for exaple: http://zadane.pl/zadanie/3361651 (there's one mistake tho, it should be "Miejscownik:(Ms):o dwojgu oczu"). I hope I cleared it just a little bit for you. If you have any more questions or would like to practice with native just text me. :)
I believe such weird forms of some words (particularly for parts of human body that go in pairs, like dwoje oczu, uszu, rąk) are a remnant of something called the dual number which existed in Proto-Slavic beside singular and plural. It prevailed in certain forms and expressions or proverbs, e.g.: "Mądrej głowie dość dwie słowie" (literally: two words are enough for the wise; now we would say "dwa słowa").
It's actually quite a complex topic because there are cases where only single forms of a single word (like one particular declension case) were influenced by that while other were not. So I think there is no point in trying to make much sense out of it but just learn it as exceptions. Note that some of those forms are stuck in the language and are the only possible choice while other are optional (dwoje rąk / dwie ręce).
Vibi106 explained very well practical aspects of it, I just wanted to add some facts (a bit trivia) so that it doesn't seem completely random and complicated. :)
A small addendum: because of that "liczba podwójna" (dual number), it is correct to say about body parts using these old forms. However, there are objects with the same names, but only plural form is used with them, e.g.:
- a human has two ears ("dwoje uszu", double number), but a pot has two lugs ("dwa ucha", plural of "ucho"; ear and lug is the same word in Polish)
- a human has two eyes ("dwoje oczu", double number), but in the broth there are drops of fat ("oka tłuszczu", plural of "oko", which in Polish is the same word as eye)