The phrase "до скольки" or "до скольких". What is more correct?

Hello, dear student! Today I would like to talk about such important aspect as the phrase "до скольки" [do skal'ki] and "до скольких" [do skal'kix]. The thing is that we have faced quite difficult topic again during our study with students. This topic is difficult not only for foreigners but also for native speakers. The topic is about the proper usage of the above-mentioned phrase which we use almost every day in the situations when we want to know open hours of any shops or cafes. We can even ask a person when he finishes his working day or we want, for example, to get information about the duration of any class - it turns out, it's not so easy. The point is that in fact there is no such form in Russian as "до скольки" [do skal'ki]. It is common in colloquial speech but actually the phrase in not correct but few people think about this fact. So what should you say and how make other people understand you?

According to the rules of the Russian language, it is necessary to use in speech the phrase "до скольких". Please, pay your attention to the stress, it should fall upon the letter -o [o]:

- До скО΄льких ты работаешь? [Da skOl'kikh ty rabotaish?] - When do you finish your working day?

- Даже не знаю, думаю, до 4 часов дня [Dazhe ne znayu, dumayu, do chetyryokh chasov dnya] - Actually, I don't know, I think until 4 p.m.

If you have any doubts and difficulties in memorizing this phrase or you are afraid that people can misunderstand you (because not all Russian-speaking people know this rule), it would be easier for you to memorize the following phrase: "до которого часа?" [do katorava chasa?].

- До которого часа работает этот магазин? [Do katorava chasa rabotait ekhtat magazin?] - What time does this store close?

- Мы закрываем магазин в 10 часов вечера [My zakryvaem magazin v desit' chasof vechira] - We are open until 10 p.m.

There are also other variations of the phrase "до скОльких" [do skol'kikh]. The rule is the same here - the stress falls upon the letter -o [o]:

Во/в скОльких: В скОльких штатах идет снег? [V skOl'kikh shtatakh idyot snek?] - In how many states is it snowing there?

Со/с скОльких Со скОльких начинает работу ваш офис? [Sa sOl'kikh nachinait rabotu vash ofis?] From what time does your office start its work?

Ко/к скОльким К скОльким мне подъехать к вам?[K skOl'kim mne pad''ekhat' k vam?] When should I come?

На скОльких На скОльких людей рассчитано блюдо? [Na skOl'kikh lyudej rasshitana blyuda?] How many people could try this meal?

So why do we have such mishmash then? And how to understand whether this phrase is correct in terms of grammar or not? Let's turn to our favorite process of declension. "Сколько" [skol'ka] is a numeral pronoun which can be declined in cases and depends on a noun which is used with it.

There are the following forms of the pronoun "сколько" in the Russian language:

Nom. case: сколько [skol'lka]
Gen. скОльких [skol'kikh]
Acc. скОльких [skol'kikh]
Dat. скОльким [skol'kim]
Inst. скОлькими [skol'kimi]
Prep. о скОльких [a skol'kikh]

That's why we use the phrase "сколько" exactly in the form that is described above.