Daisy discovers that the amount of time it takes her to drive to work is normally with:?

mean of 30 minutes and a standard deviation of 7 minutes. At what time should Daisy leave her home so that she has a 90 % chance of arriving at work by 9 AM ?

Daisy discovers that the amount of time it takes her to drive to work is normally with:?
Let t = time it actually takes her to get to work





Then t ~ N(30, 7^2)





Let T = amount of time before 9AM that she would like to leave home.





We wish to find T such that P(t%26lt;T) = 0.9


or P(z %26lt; [T-30]/7) = 0.9





Looking at the normal distribution tables,


This z value = 1.28


So (T-30)/7 = 1.28


T = 39 mins.





She must leave 39 mins before 9 AM to have a 90% chance of being at work on time.
Reply:Deviation is 7. Meaning -7 should leave by 8:30. Subtract by -7. Answer 8:23.