on a given day in october the number of customers that visit

on a given day in october, the number of customers that visit hannah\'s haunted house is normally distributed with a mean of 85 and a variance of 400. what is the probability that the number of customers on one day is between 75 and 100?

Solution

P(75 < X < 100)

= P(X < 100) - P(X < 75)

= P( Z < 100-85/400) - P(Z < 75 -85/400)

= P(Z < 0.0375) - P(Z < -0.025)

= 0.5150 - 0.49

= 0.025