In your math class you have scores of 90,82.87, and 79 on exams.. What score do you need to get on the last exam to have a mean of 86?

Question

There is one exam which will be counted twice toward your overall grade. 

Answer 1

WHICH SCORE COUNTS TWICE??

In order to do this properly you need to know that...

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The mean is the arithmetic average of the numbers

 

As a direct problem, ignoring the score that counts twice,

you would do the following:

 

 

(90+82+87+79+x)/5 = 86

(338+x)/5 = 86

 

Solve for x

 

338 +x = 86(5)

x = 430 - 338

x = 92

 

With the information given you would need a score of 92% to

have a mean of 86.   However, you failed to mention which

score would count twice, so this needs to be adjusted.

Answer 2

Hi Ronda,

 

To get a mean of 86 after taking five exams, the score on the last exam be F for final

(90 + 82+ 87+ 79 + F)/5 = 86

338 + F = 430

          F = 92

If you have to replace the lowest score 79 by the highest score 90,  

(90 + 90 + 82 + 87 + F)/5 = 86

349 + F =430

       F = 81

If no exam is used twice you need to score 92 on the last exam to average 86, if the lowest grade is replaced by the best grade so far (best score counted twice) you will need last exam score of 81.