Question

the shelf life of fresh bread has a mean of 6 days with a standard deviation of 1/2 of a day. what percent of loaves at the bakery would be expected to spoil before 5 days?

Answer 1

Since you're looking at 2 standard deviations from the mean, you follow the 66 95 rule which says 95 % of the data is within 2 standard deviations.  however you just need half of that since the other half is on the other side of the data meaning it last longer than 7 days.  So 2.5% is the answer.