# A (probably easy) math question. **URL:** \ **Category:** Factual Questions\ **Created:** [June 11, 2012, 3:48am UTC](https://boards.straightdope.com/t/a-probably-easy-math-question/624785 "2012-06-11T03:48:46Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Lancia](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lancia/32/17174_2.png) [@Lancia](https://boards.straightdope.com/u/Lancia)\ **Post date:** [June 11, 2012, 3:48am UTC](https://boards.straightdope.com/t/a-probably-easy-math-question/624785/1 "2012-06-11T03:48:46Z")
No, this isn’t homework and no, you aren’t helping me figure out my / my friends grades. I’ve seen this done a lot in college classes, and am just curious how an instructor makes these calculations. Let’s say a college student is taking some random class, with the grading as follows: Notebook/journal keeping: 10% Research paper: 20% Midterm: 30% Final: 30% Class attendance/ group discussion 10% So, at the end of the term but BEFORE the final and notebooks are graded this student has, say, a 90% overall in the class. So, 60% of the work done so far has earned him/her a 90%. Let’s say that the notebook is crap and gets a 0% and the final test earns, say an 85%. What’s the formula to figure out what the final grade (%) will be? What if the notebook grade changes to a 25% or 50% or whatever%, or the final test grade changes? ---
**Author:** ![Munch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/munch/32/5281_2.png) [@Munch](https://boards.straightdope.com/u/Munch)\ **Post date:** [June 11, 2012, 4:06am UTC](https://boards.straightdope.com/t/a-probably-easy-math-question/624785/2 "2012-06-11T04:06:13Z")
> [@](#): > > So, at the end of the term but BEFORE the final and notebooks are graded this student has, say, a 90% overall in the class. 90% of 60 is 54% (of the entire class). > [@](#): > > the final test earns, say an 85%. 85% of 30 is 25.5 points, added to the 54% is 79.5%. > [@](#): > > What if the notebook grade changes to a 25% or 50% or whatever% 25% of 10 is 2.5 points. 50% would be 5 points. Add that to the 79.5%. > [@](#): > > What’s the formula to figure out what the final grade (%) will be? Each component’s grade is multiplied by the points for each component. (Getting a 76% on the final would get you 76%\*30 = 22.8). Then just add them up. ---
**Author:** ![Wendell\_Wagner](https://avatars.discourse-cdn.com/v4/letter/w/8491ac/32.png) [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)\ **Post date:** [June 11, 2012, 4:07am UTC](https://boards.straightdope.com/t/a-probably-easy-math-question/624785/3 "2012-06-11T04:07:56Z")
So apparently you’re claiming that the research paper (20%), the midterm (30%), and class attendance/group discussion (10%) are collectively at a 90 out of a 100 level. This says that 60% of the grade is at a 90 out of 100 level. You’re also saying that the notebook (10%) is at a 0 out of 100 level and the final (30%) is a a 85 out of 100 level. So then the following equation should give us the overall grade (100%): (60% times 90) + (10% times 0) + (30% times 85) = 100% times (Overall Grade) That reduces to this: (.6 times 90) + (.1 times 0) + (.3 times 85) = 1 times (Overall Grade) That reduces to this: 54 + 0 + 25.5 = Overall Grade So the overall grade is 79.5 out of 100. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [June 11, 2012, 10:49pm UTC](https://boards.straightdope.com/t/a-probably-easy-math-question/624785/4 "2012-06-11T22:49:08Z")
> [@Lancia](#): > > What’s the formula The general formula would be: Final grade = The sum of [Score \* WeightingFactor] for each performance component ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [June 11, 2012, 10:54pm UTC](https://boards.straightdope.com/t/a-probably-easy-math-question/624785/5 "2012-06-11T22:54:48Z")
This is what’s known as a [weighted mean](http://en.wikipedia.org/wiki/Weighted_mean) (or average).