# Average

Average is some time called arithmatic mean and denoted by AM.

**AM/Average = Sum of all observations / Number of Observations**

We can re-arrange the above formula to find out sum of all observtions, if number of observations and average is given.

**Sum of all observations = Average / Number of observations**

Similarly, we can re-arrange the formula to find number of observtions if sum of all observation and average of numbers is given.

**Number of observations = Sum of all obserations / Average**

**Example: Find the average of 5, 8, 7, 9, 11**

Solution:

Sum of all observations: 5 + 8 + 7 + 9 + 11 = 40

Total numbers of observations = 5

Average = 40 / 5 = 8

**Example: Sum of observation is 40, and average is 8, find number of observations.**

Number of observations = 40 / 8 = 5

**Example: Number of observation is 5, and average is 8, find sum of observations.**

Sum of observation = 5 * 8 = 40