Which ones are unit rates
1. 15ft/1minutes
2.60 miles per hour
3.$12/2hours
4.6 bottles for 10 dollers
5. $23/1 hour
6. 40 pages in 3 ays

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”?