On the right is some data. In a set of data, the number of times a data appears is called weight. The weight can also be a percentage.

For example, when the school calculates the final grade, the mid-term exam accounts for 30%, the final exam accounts for 50%, and the homework accounts for 20%. If someone takes a midterm exam of 84 and a final exam of 92, the homework score is 9 1, and if it is an arithmetic average, it is (84+92+91)/3 = 89;

If the weighted average is found, the weighted average is 84 * 30%+92 * 50%+91* 20% = 89.4;

Mid-term exams account for 30%, final exams account for 50%, and homework accounts for 20%, which is the right of these projects.

Arithmetic average is a special form of average (its particularity lies in the equal weight of each term). In practical problems, when the weights are not equal, the average value is calculated by weighted average, and when the weights are equal, the average value is calculated by arithmetic average. The two should not be confused.