SOLUTION: After four geometry tests this nine weeks, Jessica's average score is 88%. What score does she need on her next test in order to raise her average to 90%?

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Question 284162: After four geometry tests this nine weeks, Jessica's average score is 88%. What score does she need on her next test in order to raise her average to 90%?
Found 2 solutions by stanbon, oberobic:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
After four geometry tests this nine weeks, Jessica's average score is 88%. What score does she need on her next test in order to raise her average to 90%?
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Points needed to average 90 on the 5 tests: 5*90 = 450
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Points she has on the 1st 4 tests: 4*88 = 352
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Points she needs on the 5th test: 450-352 = 98
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Using an Equation:
(4*88+x)/5 = 90
352+x = 450
x = 98
Cheers,
Stan H.

Answer by oberobic(2304) About Me  (Show Source):
You can put this solution on YOUR website!
An average of 88% means that the sum of the four tests divided by 4 = .88 = 88%.
S = sum of the 4 scores
S/4 = 88
S = 4*88
S = 352
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We need to find the value of the 'next' test that will bring the average to 90%.
.
(352+x)/5 = 90
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Multiply both sides by 5 to eliminate the denominator
352 + x = 450
x = 450 - 352 = 98
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So, the student needs to score 98% on the fifth test to pull the average up to 90%.
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Check by computing the average...
352 + 98 = 450
450 / 5 = 90
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Answer: The student needs to score 98% on the fifth test to bring the average up to 90%.
.
Done.