Define arithmetic mean?

In any given set, the mean is the average, which is the total of the numbers divided by how many numbers there are.

Ex. (10, 17, 20, 45, 68)

68 + 45 + 20 + 17 + 10 = 160

There are 5 numbers in this set.

160 ÷ 5 = 32

The mean is 32.