SOLUTION: Latisha wants a average of 86% in history class. Her past scores are 90%, 82%, 81%. If this test is double points. What percent does she need to get a average of 86%? On my homewor

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Question 1073026: Latisha wants a average of 86% in history class. Her past scores are 90%, 82%, 81%. If this test is double points. What percent does she need to get a average of 86%? On my homework help it says divide the number by 5 but I think it should be 4 since there is 4 tests. I have tried guessing and checking and I am truly puzzled. Please help! :)
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Latisha wants a average of 86% in history class.
Her past scores are 90%, 82%, 81%.
If this test is double points.
What percent does she need to get a average of 86%?
:
The reason they divide by 5 is because the last test counts "double" on her average, therefore we treat it like two test
:
let x = the score on the last test
%28%2890+%2B+82+%2B+81+%2B+2x%29%29%2F5 = 86
multiply both sides by 5, add up the scores
253 + 2x = 5(86)
2x = 430 - 253
2x = 177
x = 177/2
x = 88.5 would give her a 86% average