In this lesson, I will show you average if and weighted averages. The first thing that we'll notice is that we have points of what they're worth. We have points that are earned and a simple average does not work because each type has a weight. So in other words, 10 points for homework is not worth the same as 10 points in the final. And if we do an average, a regular average, our points come off as an absolute disappointment to the students. So what we're going to do is first we're going to do the sum if and see what the possible points are for each type of assignments. Remember, the range of the criteria go together. And finally we have the sum range which is what we're going to sum, based upon our previously defined criteria, and there it is. We're gonna do the same thing with the points earned this time. And there we are. So on the homework, the student earned 81%. Next we'll do the quiz and we have 80% that the student has earned on the quiz. You will notice our divide by zero errors which occur if we are dividing by something that is zero. If we take a look at the formula for here we are dividing D 18 which is in blue, by C 18, which is in red, and C 18 is zero. That will produce a divide by zero error. It does not matter if you physically put in the number zero, if it's empty or if it's zero, you cannot divide it by zero. That is a mathematical error, and we will proceed, we'll do it our midterm and final. And you notice once we have the number that's being divided by filled the number now becomes zero because zero divided by any number is zero. And on the midterm we have 92% job well done. And finally, for the final, please notice the range and the criteria, they go together. The criterion must be whether the first range defined in this formula. And finally, we do the sum range, and there it is. Now what we're going to do is we're going to transfer these values over to here. And we'll notice there is no project in this term. So that will be a zero. And there is the final grade. The final grade you will notice the function is called sum product. And it takes the earned, weighted, and it divides it by the sum of the weighted. So we take the earned, the weighted and we divide it by the sum of the weighted. And there it is, to review, this is used when not all averages are equal. It is used when it comes to grading performances. It is also used in finance and accounting to judge what is the best use of resources to produce the best results. Thanks for watching. Stay tuned for the next lesson where I will show you filtering based upon ranges.