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Mean - Problem 2

Teacher/Instructor Alissa Fong
Alissa Fong

MA, Stanford University
Teaching in the San Francisco Bay Area

Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts

If you guys choose to do sports in high school, you’re going to find out that usually they have a GPA eligibility requirement. Like in my school where I teach students have to maintain a 2.0 GPA or better to play in sports teams and a lot of times students say well I don’t know what my GPA is, this is how you can figure out.

GPA you might know stands for Grade Point Average. It’s an average or a mean. Here is how it’s calculated. When finding a GPA an A represents 4 points, a B represents 3 points, a C is 2 points, and D is 1 point, F is no points. Look out guys no Fs. What would the GPA be for a student who earned 4 Bs, 2 Cs, and 1 D? This is really what your schools do guys, this is Math in the real world. We’re going to find out like would this student be still eligible for sport or something or maybe their parent say in order to have a computer in your room, you have to maintain whatever, whatever GPA. This is how you can calculate it.

Okay we have to figure out how we can turn these letters into numbers. We know that a B is 3 points, so well this guy is going to get 3 points times 4 because he’s got 4 Bs. Then a C represents 2 points and he gets 2 of them. Those were his Bs, those were his Cs, and what else do we have? A D is 1 point and he has 1 D. Okay so this represents the numeric values of his grades. 4 times 3 is 12, 2 times 2 is 4 and then 1 times 1 is 1.

I’m adding these together because that’s the way we take an average or a mean. The way to calculate a mean is to add up all your numbers and then divide by how many numbers you have. And this is tricky because it looks like I only have 3 numbers right? I’m only adding together the 3 so I should maybe put 3 in the denominator here. Actually you have to be careful. The number of numbers we started with was 1 for every one of his classes. He had 4, 5, 6, 7 classes. We’re finding the average for all 7 of those classes. Again that’s really tricky it’s not just the 3 numbers I’m adding together, remember that I multiplied by stuff and what I’m dividing by is his average. I’m finding his average based on his 7 classes.

So let’s go through and do that calculation 12 plus 4 plus 1 is 17 and I need to do 17 divide by 7 and I’ll see his GPA is 2.43. That’s pretty good. At my school that would mean the student could play in a sport.

So you guys practice this. Try this with your own grades. Figure out what your grades are currently in each class, use these point values they’re the same at every school. The only trick is that sometimes if you’re in an honors class it might be different, you have to ask your counselor, but usually you use these point values, add them altogether and divide by how many classes you’re taking.

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