The physical plant at the main campus of a large state university recieves daily requests to replace florecent lightbulbs. The distribution of the number of daily requests is bell- shaped and has a mean of 41 and a standard deviation of 7. Using the 68-95-99.7 rule, what is the approximate percentage of lightbulb replacement requests numbering between 27 and 41? Do not enter the percent symbol. ans =

The age of student at a university are normally distributed with a mean of 20. What percentage of the student body is at least 20 years old?

Last year, the revenue for financial services companies had a mean of 7070 million dollars with a standard deviation of 1818 million. Find the percentage of companies with revenue between 5050 million and 9090 million dollars. Assume that the distribution is normal. Round your answer to the nearest hundredth.

According to the Department of Education the mean number of hours college students spend studying each week follows a normal distribution with a mean of 20 hours and standard deviation of 9 hours. What ‘hours of study’ represents the 90th percentile?           What ‘hours of study’ represents the 15th percentile?