Arithmetic Grade Four

Lesson Seventy-nine: Computing Averages

Finding Averages of Four Numbers - To find the average of four numbers you first find their sum and then you divide this sum by four. 

     Compute the average: 28, 25, 27, 23.

     STEP ONE: 28 + 25 + 27 + 23 = 103

     STEP TWO: 103 / 4 = 25 3/4
Here's another example: 

     Compute the average: 19, 18, 21, 20.

     STEP ONE: 19 + 18 + 21 + 20 = 78

     STEP TWO: 78 / 4 = 39 2/4

     REDUCE: 39 2/4 = 39 1/2
Finding Averages of Five Numbers: - To find the average of five numbers you first find their sum and then divide this sum by five. 

     Compute the average: 12, 13, 11, 10, 11.

     STEP ONE: 12 + 13 + 11 + 10 + 10 = 56 

     STEP TWO: 56 / 5 = 11 1/5
Here's another example: 

     Compute the average: 33, 33, 27, 35, 26.

     STEP ONE: 33 + 33 + 27 + 35 + 26 = 154

     STEP TWO: 154 / 5 = 30 4/5
Finding the Average of Any Number of Numbers - To find the average of a list of numbers you first find the sum of the numbers in the list. Then you divide this sum by the number of numbers in the list. Here's an example with nine numbers in a list. 

     Compute the average: 3, 7, 4, 6, 8, 4, 5, 3, 2.

     STEP ONE: 3 + 7 + 4 + 6 + 8 + 4 + 5 + 3 +2 = 42

     STEP TWO: 42 / 9 = 4 6/9

     REDUCE:  4 6/9 = 4 2/3
You get to try a few for yourself on the next page.

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