To calculate the percentile test score, all you need to do is divide the earned points by the total points possible. In other words, you're simply finding the percentage of good answers:
1)percentage score = #correct / #total
2)As #correct + #wrong = #total, we can write the equation also as:
percentage score = (#total - #wrong) / #total
3)Then, all you need to do is convert the percentage score into a letter grade.
