Grade Averages

Date: 11/16/95 at 18:32:41
From: Fortino Martinez
Subject: Averaging grades

If Johnny has a 82% average for the 1st 9wks and a 75% average for the 
2nd 9wks, what grade would he have to get on the final to recieve 80% 
semester grade in this class.  The grades are weighted as follows: each 
9wks 40 % and the semester test 20%.

K Riggins CCHS

Date: 11/19/95 at 15:4:26
From: Doctor Ethan
Subject: Re: Averaging grades

Okay, good question.

  Here is how it works.

.4 +.4 + .2 = 1

So what we are going to do is to set up an equation involving the 
percentages of the present grades and how they add up.  It looks like 
this:

 .4(82) + .4(75) + .2 (XX) = 80


So to solve for XX  we simplify to 

32.8 + 30 + .2(XX) = 80 

SO.....

.2(XX) = 80 - 32.8 - 30 

So .2(XX) = 17.2

Now divide both sides by .2

and XX = 86.

Hope that helps.

-Doctor Ethan,  The Geometry Forum