The average (arithmetic mean) is equal to the sum of the n numbers divided by n:
Average = (a1+a2+...+an) / n
The average of 1,2,5 is:
Average = (1+2+5) / 3 = 2.667
The average of a set of numbers is simply the sum of the numbers divided by the total number of values in the set. For example, suppose we want the average of 24 , 55 , 17 , 87 and 100 . Simply find the sum of the numbers: 24 + 55 + 17 + 87 + 100 = 283 and divide by 5 to get 56.6 .
The mean x̄ of a data set is the sum of all of the data values divided by the count or size n.