noun
Mathematical term for the arithmetic mean or average of a set of numbers.
このデータの中数を求めなさい。
Find the mean of this data.
noun
middle-school arithmetic
Abbreviation of 中学 (middle school) and 算数 (arithmetic). Used in educational contexts, such as exam preparation materials.
塾で中数を教えている。
I teach middle-school arithmetic at a cram school.
算数 is the standard term for elementary/middle-school arithmetic. 中数 is an abbreviation used in certain contexts.
Sense 1 is a direct use of the kanji 中 (middle) and 数 (number) to mean 'mean' or 'average'. Sense 2 is an abbreviation of 中学 (middle school) and 算数 (arithmetic).