Thats interestesting.
An "A+" in the US means all problems are completed and correct.
A "F" in the US means 1 of 2 things. Not handed in, or Below 50% of your anwsers are wrong.
All grades from the semester are averaged; So say I got 2 A+ and 2 F. My average would be a C. C is considered average. Now wherever your average grade lines up on the grade point average scale is what your GPA is.
A = Excelent
B = Above Average
C = Average
D = Below Average
F = Failure
Also by the way, I'm a staight A student in to US. For Math and Science I mantain 92% and For Social Studies and English, I have a 99%
Jake