The mean is the average of a set of numbers. It is the sum of all the items in a set, divided by the total number of items in the set.

A group of numbers can be referred to as a set.

Example: 15, 4, 37, 18, 11.

Mean of two numbers:

When there are only two numbers, the mean is easy to find. It is simply the number that is halfway between the two numbers of the set.

Example:

In this example, the set is: 10, 40.

Here, 25 is halfway between 10 and 40, so it is the mean.
Another way to find the mean, or average, is to find the sum of the numbers and divide by 2:

Mean of more than two numbers:
Consider the set: 10, 16, 40.
Here, find the sum of the three numbers and divide by the total numbers in the set, which is three.

Thus, the mean or average, is 22.

Mean in real life:
Example: There is a family with three kids and their ages are: 1, 3, and 5. To find out the mean age of all of the kids in the family, we would, add together all of their ages:
1 + 3 + 5 = 9
and then we would divide that number by the total number of kids.
9 ÷ 3 = 3
The kids in this family have a mean age of 3.