Eight-grade mathematics begins to learn five chapters: quadratic root, pythagorean theorem, parallelogram, linear function and data analysis in the next semester. Data analysis includes weighted average.
The formula of weighted average is: average value = (k1* a1+k2 * a2+k3 * a3+...+kn * an)/(k1+k2+k3+...+kn).
Among them, the coefficient (K 1, K2, K3, ... kn) is weighted, which shows the proportion of the data behind this coefficient in the whole statistical data and the influence of this data on the statistical results.