How to calculate an Average  
The "mean" or "average" is found by adding a group of values to get the sum and dividing the sum of values by the number of values.
9, 8, 10, 8, 10 here's how: first add 9 + 8 + 10 + 8 + 10 = 45, divide by the number of values added. (5) 45 ÷ 5 = 9 So the mean or average quiz score would be 9!
