A score of 64 out of 100 corresponds to a grade of D on the majority of grading schemes. This grade corresponds to one grade point on the scale used to calculate the grade point average.
The majority of American educational standards provide letter grades to each number grade based on a scale of 1 to 100. The grade letters are as follows:
A = 90 to 100
B equals 80 to 90 C equals 70 to 80 D equals 60 to 70 F equals 0 to 60
Some schools also assign grades using the plus and minus signs. For example, a score of 72 out of 100 corresponds to a C-, while a score of 78 out of 100 corresponds to a C+.