What Is Weighted Average?
A weighted average multiplies each value by its own weight (its relative importance), adds those products together, and divides by the total weight — instead of treating every value equally like a regular average does. It's used whenever some data points should count more, like a course grade where the final exam is worth more than a homework assignment.
Example
A grade of 90 weighted 20% and a grade of 70 weighted 80% gives a weighted average of (90×0.2) + (70×0.8) = 18 + 56 = 74, not the plain average of 80.