SOLUTION: If my average mark is 59%, and I get a 90% on my test, what will my new average be?

Question 531116: If my average mark is 59%, and I get a 90% on my test, what will my new average be?
Answer by lmeeks54(111) (Show Source): You can put this solution on YOUR website!
From the data given, this question cannot be answered. That is, when we think about averaging a series of values (e.g., school work/exam scores), and then determining how the average will change with some new potential score, the total number of values being considered in the average calculation is important.
...
Take a couple of simple experiments to test this notion. Assume there are only two prior grades:
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57%
61%
...
The average of these two is 59.0%. Now add a third score: 90%
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57%
61%
90%
...
The average of these three scores is 69.3%. That is a jump in class average of >10% for adding that single 90% score.
...
Now consider a 15-week course that meets 3 times per week, and that for each class meeting there is a daily quiz or homework grade. Then for the 1st 44 weeks, if the average of all grades is 59%, adding one 90% grade will not even change the final average to 60%...
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Thus, the number of values being considered makes an important difference in the final average. This could be further complicated by the fact that in many school settings, not all assignments/activities might be weighted equally. We have no information in this problem statement about weighting the average; however, that is often how grades are calculated.
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cheers,
Lee
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