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The arithmetic mean of n numbers a_1, a_2, ... , a_n equals am = (a_1 + a_2 + ... + a_n) / n. Example: The arithmetic mean of 2, 5, 4, 1, 2, 3 is am = (2 + 5 + 4 + 1 + 2 + 3) / 6 = 17 / 6 ≈ 2.8