"Weight" is a mathematical concept. Explain this word separately first. "Add" means "multiply". The popular understanding of "weight" is "coefficient", and this coefficient is called "weight". So "weighting" means "multiplying by weight", which means "multiplying by coefficient". In mathematics, there are two calculation methods, namely "weighted average" and "additive average". When the "weights" are the same, the calculated values of the added average and the weighted average are the same. Because the "weights" are different in some cases, the calculated value of the added average can't reflect the true and reasonable average, so we generally adopt the weighted average at this time. For example:

A, the calculation of the known weight:

Your exam results for one academic year are: mid-term exam accounts for 30%, final exam accounts for 50%, and homework accounts for 20%. (These percentages are known weights and proportions of each period) Find the average grade of three semesters.

If you get 84 points in the mid-term exam, 92 points in the final exam, and 9 1 point in the homework exam, it is (84+92+9 1)/3=89 points.

Then the weighted average method is: 84 * 30%+92 * 50%+91* 20% = 89.4, which means that the weights are 30%, 50% and 20% when the weights are known.

Second, in the case of unknown weight?

If you participate in the competition, calculate the average score: a group of 50 people will give you 80 points; There are 60 people in the second group, and you get 82 points. On average, your score is (80+82)/2=8 1 minute. The weighted average is (50 * 80+60 * 82)/(50+60) = 81.09, which is reasonable.