# Percentages: Oops, one more thing

posted by
**day** on
.

Forgot to mention that the exams are each 10%. It's 40% because he had 4 exams.

math problem:

pedro wants to calculate his gpa.

he has the lab grades:90/100,98/100,90/100,94/100,90/100,90/100,95/100,98/100. Labs are worth 20%.

He has the test grades: 9/10,6/10,10/10,10/10,5/10,7/10,7/10,7/10,10/10,10/10,8/10,10/10. Homework is worth 20%

test grades are: 35/100, 20/100, 26/100, 34/100. Exams are worth 40%.

What is his grades so far? What would his grade be is he had a 90 on the final which is worth 20%?

I got 62 for his current grade but I am not sure

For Further Reading

mathematics (percentages) - DrBob222, Tuesday, December 5, 2006 at 6:28pm

The way I calculate it Pedro is in trouble. He hasn't made over 34% on any test he has taken and he thinks he can make 90 on the final. Probably not. However, if he did, I calculate the final average as 64.6%. As for the current average, I don't know how to calculate that because he hasn't taken the final. As an estimate, we can add the averagae of his lab scores (93.125%) + average of homework (82.5%) + (2 x avg test scores since they count twice as much at 40% (2 x 28.75) and divide by 4 to obtain 58.3%.

Have you reversed the scores for homework and test scores? I think so and my first calculation took that into account. Next, I don't think counting four test scores as 10% each or averaging them and counting the average aa 40% will change anything. I think the final answer will not change. Why don't you show us how you came up with your 62, since you aren't sure it is right or wrong, but first check out the homework vs test scores. Again, I say Pedro is in serious trouble. Frankly, I think Pedro should spend less time studying for this class and use that time to study for another class. Finally, if you take my original figure of 58.3 for the current value, multiply that by 0.8 (it represents 80% of the final grade) and add 20% of 90 (for the final), you get, VOILA, 64.6% which is the same value I obtained initially when taking all of it into account. I think I shall stick with my numbers, assuming you have reversed the test and homework scores. (Actually, you didn't reverse anything; however, you talk about test scores but list what I think are homework scores which leaves the implication that those are test scores.)

Since the test are 10% each, (it said in the text that the test are 10% each thus being 40%). I added up all the test scores times what ever I got out of 100 by .20, and times 100 by .20. and divide the values, and times it by 100. I don't know, I still think 58% is too low because test are 40% (10% each), labs are 20%, homework is 20%, and exam is 20%. Homework, labs, and final is 60% total and the exams are 40%=100%.

my calculations:

labs: 745 (x.20)/800 (.20)=149/160=93.125

exams:35(.10)+20(.10)+34(.10)+26(.10)/40=28.75

homework: 99/120 (x.20)=82.5

add them up I got 68 that time when I multiplied all the exams by 10%. When I times it by 40%, I got 62%.

lab work=93.125*0.20=18.625

homewrk=82.5*0.2=16.5

tests=28.75*0.4=11.5

NOW, (93.125+82.5+28.75)/(3) =

204.375/3=68.125 which is how you obtained 68. But that isn't right because this assigns equal weight to each of the three items.

It is done this way: 80% of the score comes from 20%+20%+40%(that is 10%+10%+10%+10%)= 0.80 expressed as a decimal.

(18.625+16.5+11.5)/0.80=46.625/0.8=58.3

Just to check it out, we take 58.3 @ 80% + 90(final) @ 20% and we obtain

(58.3*0.8)+(90*0.2)/1(for 100%)= 64.6 for a final average. And 64.6 is the final score if you take the (average homework*0.2)+(avg test*0.4)+(avg lab*0.2)+(final*0.2)=64.6

But I don't think you were suppose to multiple each test grade by 10%, not 40%.

I think it's also wrong because the homework and labs together do weigh the same as the test total.

day: You are wrong on these two last items. DrBob is right. You keep saying "I don't think...". Maybe the problem is you are looking to prove what you did was right, instead of looking for the logic of what someone is teaching you.

I suggest a tutor on this if you still are having difficulty, this material is basic to many things in the future. Discuss a tutor with your mom.

But I've checked with my teacher and Dr.Bob's explanation is wrong. I'm getting two separate explanations, one from my teacher and another from Dr.Bob. I wasn't trying to be rude, I was frustrated and his math just didn't make sense to me. If I offended anyone I apologize. I wasn't trying to be thick skinned but if you can't handle people who don't get your calculations and what not, maybe you should not be here.

Day--Nor was anyone accusing you of being rude. It is tough to get two answers and not know which is correct. I think what I have posted is correct but the problem may be that your interpretation of the data may be different than mine because it may not be presented in your post the same as your teacher presented it to you. That happens and it happens more than you may think. I've never understood from the beginning exactly what you think is wrong and what you think is right about my calculations. A couple of quick questions. Does the final number (65% rounded), assuming Pedro makes 90% on the final, agree with you and your teacher? To my knowledge, that has never been addressed. Please show how that was obtained.(I'm asking to determine if we have two disageements or just one.) Second, please give a detailed explanation of the two calculations (in math, not in writing), for how you think it(both current and final avg assuming 90% on the final) should be done. I guess a third choice is to drop the whole thing and assume you and your teacher are correct. In any event, we appreciate you using Jiskha for homework help and hope you will come again.

I respect your calculation fully, I am just tied between the twp explanations. I am sure it's right, maybe there are different ways to calculate it? I don't know. I appreciate you answering my question and replying in the most mature manner. I will figure it out and I too feel the need to drop this because this is a site for homework help, not arguments.

Have a Nice Day

Day

OK. That't fine. One final note which is a standard with me. Use your teacher's notes and work. That's where yuor grade is coming from. Then look at other resources if and when you have time to examine the issue further. And we were not arguing. We were discussing an issue. Thanks for using Jiskha.