How do we decide if 中 is ちゅう or じゅう ?
For example, in this sentence １０人中３人はビデオを持っている which pronunciation should we use?
What about this: そのピアニストの演奏中、彼らは一心に耳を傾けた。
一年中【いちねんじゅう】 all year
一日中【いちにちじゅう】 all day
世界中【せかいじゅう】 all over the world
午前中【ごぜんちゅう】 [at some point] during morning
会議中【かいぎちゅう】 in a meeting [e.g. "he is in a meeting at the moment"]
Note that in some cases, both can be used and the only way to tell would be from context (e.g. an expression followed by に is more likely to be ちゅう) or in speech:
来月中【らいげつじゅう】 all of next month
来月中【らいげつちゅう】 [some time] next month
"out of" is 「ちゅう」, "through" is 「じゅう」.
(suf,abbr,n-suf) medium; average; middle; moderation; middle school; China; in; out of (e.g. three out of ten people); during (a certain time when one did or is doing something); (P)
(suf) through; throughout; in the course of; all over or throughout (e.g. a place)
That second example is "during", so 「ちゅう」.