Let T represent the fifth test score. The average is the sum of scores divided by their number.
... 82 = (83 +75 +93 +67 +T)/5
... 410 = 318 +T . . . . . . . multiply by 5
... 92 = T . . . . . . . . . . . . subtract 318
The fifth score was 92.
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One of the ways I like to work problems like these is to add the differences from the mean. Those are ...
1, -7, 11, -15
so their sum is -10.
The final score must be 10 above the mean in order for this total to be zero. 10 above the mean is 92.
