Figuring final grade: You have a series of tests that....

joi

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Hi. The question is that you have a series of tests that are scored 57, 67, and 60. Tests are worth 80 percent of your grade. Homework counts for 20% and you have a perfect on homework. What does the final test score need to be in order for you to get a 70% in the class?

I first found the average percent of the three tests, which is 61%. I then tried to find the test score to obtain an overall 70% for the tests, and then multiplied it by .80. From here, I don't know what to do. Please help.

thanx
 
Treat the overall-grade percentage as points, so your grade is out of one hundred points.

The homework counts for twenty points. Since you have a perfect score on the homework, how many of those twenty points do you get?

You have four tests (the three already taken, plus the final), each of which is apparently weighted the same. So count each as being twenty points. You got 57% of the first twenty points. How much is that?

Add up the points from the three tests and the homework. What is your current point total?

You need seventy points overall, so subtract your current total from "70" to find out how many points you still need.

The final is worth twenty points, and you need however many points you found in the last step. Compute the percentage score that you need.

If you get stuck, please reply showing how far you have gotten in following these instructions. Thank you.

Eliz.
 
Re: Figuring final grade

joi!

I like Stapel's solution . . . Here's mine.


You have a series of tests that are scored 57, 67, and 60.
Tests are worth 80% of your grade.
Homework counts for 20% and you have a perfect on homework.
What does the final test score need to be in order for you to get a 70% in the class?

Out of the \(\displaystyle \L100\) possible points for your grade, you want \(\displaystyle \L70\) (at least).

20% of your perfect homework grade gives you \(\displaystyle \L20\) of these points.

Hence, the 80% of your test average must be the other \(\displaystyle \L50\) points.


Let \(\displaystyle x\) = your fourth test score.

The average of your four tests is: \(\displaystyle \L\;\frac{57\,+\,67\,+\,60\,+\,x}{4}\:=\:\frac{x\,+\,184}{4}\)

80% of this average is: \(\displaystyle \L\,\frac{4}{5}\,\times\,\frac{x\,+\,184}{4} \:=\:\frac{x\,+\,184}{5}\)

Since this must equal \(\displaystyle \L50\):

\(\displaystyle \L\;\;\;\frac{x\,+\,184}{5}\:=\:50\;\;\large{\Rightarrow\;\;x\,+\,184\:=\:250\;\;\Rightarrow\;\;x \:=\:66}\)

 
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