Grades in a Classroom Are Often Given According to the Percentage

Grades in a classroom are often given according to the percentage score obtained by the student. Suppose that a teacher grades according to the following scheme, where all scores are rounded to the nearest percent: A $\quad 90 \% - 100 \%$
B $80 \% - 89 \%$
C $65 \% - 79 \%$
D $50 \% - 64 \%$
$\mathrm { F } \quad 0 \% - 49 \%$ To determine a percent grade, form a ratio of score received to possible score and then write this ratio as a percent. Calculate the percent (nearest percent) and determine the letter grade for each score. The student gets 91 answers right out of a possible 100. What is the letter grade?

A) A
B) F
C) C
D) B
E) D