Weighted average is a concept of statistics. The frequency at which a number appears in a set of data is called weight. Simply put, the value multiplied by the frequency and divided by the total number is the weighted average.

The weighted average is that each number is multiplied by its share, and then their sum is divided by the number of these numbers.

For example, 5.6.7.8's shares are 20%, 15%, 30% and 35% respectively.

The weighted average is (5 * 20%+6 *15%+7 * 30%+8 * 35%)/4.