A car rental has cars with an average of 9000 miles and stan

A car rental has cars with an average of 9000 miles and standard deviation of 1200. If 25 cars are in a lot, what is the probability there average miles will be less than 9500 miles?

Solution

So the probability there average miles will be less than 9500 miles is

P(xbar<9500) = P((xbar-mean)/(s/vn) <(9500-9000)/(1200/sqrt(25)))

=P(Z<2.08)

=0.9812 (from standard normal table)