Question 1208697
<br>
The response from the other tutor shows a straightforward solution using the standard method for determining the average.<br>
When the numbers being averaged are "close together", it is sometimes faster and easier to work with the "overs" and "unders" instead of with the numbers themselves.<br>
See if this solution method "works" for you.<br>
Compare each test score to the desired average of 80:<br><pre>

   1  80   0
   2  83  +3
   3  71  -9
   4  61 -19
   5  95 +15
 ------------
  total  -10</pre>
With his 5 tests, he is a total of 10 points short of his desired average, so he must make up those 10 points on the final.  Then, since the final counts twice as much as each test, his score on the final must be 10/2 = 5 points above the desired average.<br>
So his score on the final must be 85 to get an overall average of 80.<br>
ANSWER: 85<br>