"How long will it take?"
Yes, for i read it in the book " Learn to read in Japanese " by Roger Lake and Noriko Ura wherein " どのくらいかかりますか " is used. A very useful book to learn japanese.
No, if there is a word following the こ・そ・あ・ど word, it needs to have the の ending. If it is followed by a particle, then it can use れ. In casual usage neither is incorrect, but どのぐらい is by far the more accepted version.
then how do we distinguish 'how much does it cost' and 'how long does it take'?
It is purely by context. Or if you want to make it explicit
- どれくらい お金（かね）が かかりますか (How much is the cost)
- どれくらい 時間（じかん）が かかりますか (How long does it take)
My dictionary says どれくらい for "how long..." Doesn't say if there is a distinction between lenghts of duration and lengths of things though.
どれくらい can mean different types of "how much." Samples below taken from top google searches
- 髪の毛は1ヶ月でどれくらい伸びる？ (How much does one's hair grow in a month?)
- 1TBとはどれくらいの容量ですか？ (How much capacity is 1 TB?)
- 宇宙はどれくらい広いの？ (How large is the universe?)
Is there an implicit "about/approximately" with くらい ? In another example in this lesson it says 十分くらいかかります translates to "about ten minutes"
Is 何時間かかりますか an acceptable translation and if so are there nuances that makes one more suitable than the other?
I know that's the literal translation, but I was wondering if idiomatically or colloquially it was used otherwise. This is based on a previous question 彼らは何時間働きますか for which duo gives the translation as something like "how long do they work for?"
A lot of interpretive rather than literal translations are accepted in the Japanese course. I think if you submitted an error report your translation would probably be accepted, it does mean the same thing, just specifying hours. Using “jikan” would not work if the expected answer is less than an hour, but the English here gives no implication of that.
We do not normally write kanji when referring to "how long/how much." But I can't say it is wrong to use 掛 in this case.
I learned from class that it is どのぐらいかかりますか？
What's the difference between どれくらい and どのぐらい (besides the dakuten and noun vs prenonoun)?
Does this actually mean about how long will it take? kurai seems to mean "approximately" in the other sentences, like if I answered "go-fun kurai kakarimasu".
To my knowledge, どれ and くらい are colloquially written in katakana.
Why is dore used instead of itsu, if dore means "which" and itsu means "when?" Wouldn't itsugurai make more sense? I'm trying to understand the reasoning behind the word choice when the language was being reformed. I just don't understand how "which" turns into "how much."
くらい means "approximate quantity" so どれくらい means which approximate quantity (i.e. how much time/quantity/etc). いつぐらい means what time approximately (when) and is different from how much.
Ahh, I see. That makes a lot of sense; thank you very much for clarifying that. :)
Please don't blindly apply kanji. The uncommon ones can confuse people. The most common version for this sentence is not to use kanji at all.