Statistic student return and forgot it all

[yeungmei]

I studied stat couple years ago, and going back again...here goes...

THe time needed to complete a final examination in a particular college course is normally distributed with a mean of 80 minutes and a standard deviation of 10 minutes.

Assume that the class has students and that the examination period is 90 mintues in length. How many students do you expect will be unable to complete the exam in the allotted time?

so, i know mean is 80 and SD is 10, and the z is 90...am i find the "n" in the case?? How do i find it? by using what formula??

 

[e(ho0n3]

I think you have to find out what percent of the normal distribution is beyond one standard deviation. Then, multiply that percentage by the amount of students taking the test and you should have your answer.