Statistics
posted by Donna .
A construction company builds apartment buildings. The construction time follows a normal distribution with a mean time of 200 days and a standard diviation of 20 days. (a) What is the probability of completing a building in 224 days or less? (b) What is the probability that it will take between 210 and 224 days to complete a building?

Z = (scoremean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions related to the Z scores.