SOLUTION: Very confused, please help if you can. A student is trying to determine what he must make on the final exam in order to achieve an 80% or higher for the final course grade. The

Algebra ->  Probability-and-statistics -> SOLUTION: Very confused, please help if you can. A student is trying to determine what he must make on the final exam in order to achieve an 80% or higher for the final course grade. The      Log On


   

Question 1081376: Very confused, please help if you can.
A student is trying to determine what he must make on the final exam in order to achieve an 80% or higher for the final course grade. The average of his four quarters grades counts 75% of his final grade and the final exam will count the other 25%. His quarter grades are 96, 84, 92, 80. What is the minimum score she can get on the final to maintain an 90 average?
92
90
96
94
Answer by math_helper(2461) About Me  (Show Source):
You can put this solution on YOUR website!
Usually, its best to write things out in terms of a variable, and then solve for that variable.
First, we can calculate the quarter grade average:
+%28%2896%2B84%2B92%2B80%29%2F4%29+%2A+0.75+=+66+ <—<< contribution of quarter grades toward final grade
—
Now let x be the score on the final
We use that 66 from above in our equation involving 'x':
++66+%2B+0.25x+=+90+
++0.25x+=+90-66+
++0.25x+=+24+
++++x+=+24%2F0.25+
++highlight%28+x+=+96+%29 <—<< Minimum score needed on final to maintain a 90 average
————————
I noticed that in one part of the question it says '80%' but the last part says 'maintain a 90 average' — these are conflicting. I gave you the work-out for 90%. Adjust accordingly if you really needed 80% for the overall final grade.