In fact, there are some very old books that show this as the average, the sum divided by two arithmetic mean, but the modern practice is to use the geometric mean.

事实上，一些很老的书籍上,平均的定义就是算数意义的，总的来说被分为两种算数意义，但现代我们多用几何意义。

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So even at my level of arithmetic that's a lot less than 30%.

就我的算数水平都知道这绝对少于30%

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There's almost an arithmetic relationship theory that they put forth.

他们提出的是基于算数关系的理论

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