Organize the data into two columns. In the left column, list the raw numbers to be averaged. In the right column, list the weight of each entry. For instance, if the problem is "Mary has taken 2 tests, 2 quizzes and a midterm this semester. She scored 89 and 91 on her tests, 85 and 83 on her quizzes, and 95 on her midterm. If the quizzes receive a weight of 2, the tests 5 and the midterm 9, what is Mary's weighted average?" your columns would appear:
89 5
91 5
85 2
83 2
95 9
Multiply each row together, and place the product in a third column to the right of the other two:
89 X 5 = 445
91 X 5 = 455
85 X 2 = 170
83 X 2 = 166
95 X 9 = 855
Add the contents of column two together:
5 + 5 + 2 + 2 + 9 = 23
Add the contents of the third column together:
445 + 455 + 170 + 166 + 855 = 2,091
Divide the sum of column three by the sum of column four to determine the weighted average:
2091 / 23 = 90.9
Mary's weighted average is 90.9 percent.