Christina's ice cream parlor sold 60 vanilla cones on the first day of summer. If the goal is to increase the number of vanilla cones sold each day by 4. how many will be sold 20 days later?
The solution is

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”?