Charley's grade in the three quarters are 85, 88, and 92. If she targets to have an average grade of greater than 90 in the four quarters this school year, what is the least grade she
should have for the fourth quarter?

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”?