Peggy was taking a timed 90-question test. she was able to correctly answer 90% of the questions but had to skip the rest. how many questions did peggy answer correctly?

Scores on a university exam are normally distributed with a mean of 78 and a standard deviation of 8. the professor teaching the class declares that a score of 70 or higher is required for a grade of at least “c.” using the 68-95-99.7 rule, what percentage of students failed to earn a grade of at least “c”?