SOLUTION: Tom has taken 5 of the 8 equally weighted tests in his U.S. History class this semester, and he has an average score of exactly 78.0 points. How many points does he need to earn on

Question 256023: Tom has taken 5 of the 8 equally weighted tests in his U.S. History class this semester, and he has an average score of exactly 78.0 points. How many points does he need to earn on the 6th test to bring his average score up to exactly 80.0 points?
A. 90 B. 88 C. 82 D. 80 E. 79

Found 2 solutions by drk, stanbon:
Answer by drk(1908) (Show Source): You can put this solution on YOUR website!
He has taken 5 tests with an average of 78. This means his total points so far is: 390.
After 6 tests he wants an average of 80, so he needs 480 total points.
This means on the 6th test, he must score 90 points: choice [A]
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Tom has taken 5 of the 8 equally weighted tests in his U.S. History class this semester, and he has an average score of exactly 78.0 points. How many points does he need to earn on the 6th test to bring his average score up to exactly 80.0 points?
---------------
Let the 6th test score be "x".
Equation:
Total points from the 1st 5 tests is 5*78 = 390
To solve for "x":
(390+x)/6 = 80
390 + x = 480
x = 90
He need a 90 on the 6th test.
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Cheers,
Stan H.

A. 90 B. 88 C. 82 D. 80 E. 79

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