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, in which all scores are rounded to the nearest percent. A 90%100% B 80%89% C 65%79% D 50%64% F 0%49% To determine a percent grade, form a ratio of score received to possible score, and then write this ratio as a percent. For example, if a student gets seven answers right out of a possible ten, his or her percent score is 7 10 = 70%. Calculate the percent (nearest percent) and determine the letter grade for the following score. Possible 100 points; earned 78 points percent % letter grade