Question 850824
If you want to know for yourself (rather than this being a math problem), there's a great little grade calculator at http://www.back2college.com/raisegpa.htm.
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Here's how to solve it:
There are a total of 500 points available in the class.
72 + 60 + x + x + x
You need to know what constitutes a C+.  Let's call it 76 for the problem's sake.  You can substitute whatever value you want in that spot.
72 + 60 + 3x = 76*5 (5 exams)
132 + 3x = 380
Subtract 132 from each side
3x = 380 - 132
3x = 258
Divide each side by 3
x = 86 (the average you'll need)