Question 183117
this one has me stumped. I don't know why, I usually can get averages, but my mind is stuck here: 
8. The final grade for a particular course is calculated by dividing total points earned by total points available. There are 120 points available in the first half of the course, and 140 points in the second half of the course. If a student earns 81% in the first half of the course, how many points must the student earn in the second half in order to earn an 80% B final grade? 
<pre><font size = 4 color = "indigo"><b>
{{{ matrix(1,3,Average, "=", (total_points_made)/(total_points_possible))}}}

81% or .81 of the 120 points available in the first half 
of the course is 97.2 points.

Let x = the number of points to make in the second half

Then total points made in both halves will be 97.2 + x

The total points available in both halves of the course is 120 + 140 = 260

{{{matrix(1,3,Average, "=", (total points_made)/(total_points_possible))}}}

We substitute .8 (the decimal equivalent of 80% for the Average

{{{ matrix(1,3, .8, "=", (97.2+x)/260  )}}}

Can you solve that equation for x?  If not post again.

Answer: 110.8

Edwin</pre>