SOLUTION: In 8 tests, Grace achieved an average of 72%. After her ninth test, she had an average of 74%. What percentage did she get for her ninth test?

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Question 852652: In 8 tests, Grace achieved an average of 72%. After her ninth test, she had an average of 74%.
What percentage did she get for her ninth test?
Answer by JulietG(1812) About Me  (Show Source):
You can put this solution on YOUR website!
In 8 tests, Grace has an average of 72. 72*8=576 out of a possible 800.
After 9 tests, there are a possible 900. .74*900=666.
If she know has 666 points, and before this last test had 576 points, what was her score on the last exam? 666-576=90.