SOLUTION: How many 75%(c) grades does it take to bribg a zero up to a C(>70%)

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Question 892267: How many 75%(c) grades does it take to bribg a zero up to a C(>70%)
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
If all grades count the same (for example, if the grades are for quizzes given equal value for the average), after a zero, n 75%(c) grades would bring the average percentage grade to
%2875%2An%2B0%29%2F%28n%2B1%29=75n%2F%28n%2B1%29%
for a 70.00%, we need 75n%2F%28n%2B1%29=70 .
Solving that equation:
75n%2F%28n%2B1%29=70 --> 75n=70%28n%2B1%29 --> 75n=70n%2B70 --> 75n-70n=70 --> 5n=70 --> n=70%2F5 --> highlight%28n=14%29 .
In practice, highlight%2813%29 75%(c) grades would do,
because a 69.50% would be rounded to 70%, and the equation would be
75n%2F%28n%2B1%29=69.5 --> 75n=69.5%28n%2B1%29 --> 75n=69.5n%2B69.5 --> 75n-69.5n=69.5 --> 5.5n=69.5 --> n=69.5%2F5.5 --> n=about+12.64 .