If you have the two separate words, it's 二日{ふつか} and 三日{みっか}. But how are they read together? ふた、みっか, に、さんにち, some combination thereof or something else entirely?
Source sentence for the curious:
アキちゃんは広いお屋敷で二、三日ゆったり過ごしてくればいいのよ。
If you have the two separate words, it's 二日{ふつか} and 三日{みっか}. But how are they read together? ふた、みっか, に、さんにち, some combination thereof or something else entirely?
Source sentence for the curious:
アキちゃんは広いお屋敷で二、三日ゆったり過ごしてくればいいのよ。
It reads に、さんにち (the comma is purely orthographic, you may or may not write it out).
Similarly, we say...
一、二日 いち、ににち
三、四日 さん、よっか ← irregular!
四、五日 し、ごにち
五、六日 ご、ろくにち
Longer span equivalents are hardly heard, perhaps because we come to use "a week" (一週間) or other higher units then, I suppose.
ふた、みっか might actually sound surprisingly comprehensible to native speakers, but it never exists.
It is read 「にさんにち」.
Colloquially, people say 「にさんち」 as well.