Grading
I grde individual assignments and questions on exams as letter grades.  For me it is more meaningful than numeric values.  When computing overall grades, however, I do convert these into numeric values. The following is the conversion of letter grades to numeric values.

A+ 99
A+/A 98
A 96
A/A- 94
A- 92
A-/B+ 90
B+ 89
B+/B 88
B 86
B/B- 84
B- 82
B-/C+ 80
C+ 79
C+/C 78
C 76
C/C- 74
C- 72
C-/D+ 70
D+ 69
D+/D 68
D 66
D/D- 64
D- 62
D-/F 60


The exact numeric values taht convert to letter grades does vary each year.  I try to find natural breaks between ranges for grades.  Typical values will look like this:
A
93+
A-
90-92
B+
88-89
B
83-87
B-
80-82
C+
78-79
C
73-77
C-
70-72
D+
68-69
D
63-67
F
62-