SOLUTION: Jane averaged her five equally weighted test grades and got 60%. This was wrong because she had entered one grade incorrectly. That incorrect score should have been entered as 80%.

Question 935758: Jane averaged her five equally weighted test grades and got 60%. This was wrong because she had entered one grade incorrectly. That incorrect score should have been entered as 80%. If she had used the 80%, her correct average for the five tests would have been 70%. What percent did she incorrectly enter instead of 80%?
Found 2 solutions by stanbon, TimothyLamb:
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Jane averaged her five equally weighted test grades and got 60%. This was wrong because she had entered one grade incorrectly. That incorrect score should have been entered as 80%. If she had used the 80%, her correct average for the five tests would have been 70%. What percent did she incorrectly enter instead of 80%?
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Equations:
4correct scores and 1 error score::
(4c + e)/5 = 60
4c + e = 300
-----------------------
5 correct scores::
(4c + 80)/5 = 70
4c + 80 = 350
-------
Solve this system:
4c + e = 300
4c + 80 = 350
-----
80-e = 50
e = 30
-----
Answer:: 30%
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Cheers,
Stan H.
Answer by TimothyLamb(4379) (Show Source): You can put this solution on YOUR website!
x = incorrect test score
y = sum of other four correct test scores
---
x + y = 60*5
80 + y = 70*5
---
put the system of linear equations into standard form
---
x + y = 300
y = 270
---
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https://sooeet.com/math/system-of-linear-equations-solver.php
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solution:
x = incorrect test score = 30
y = sum of other four correct test scores = 270
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