Approximate the probability that 100 customers can be served in less than 2 hours of total service time. The central limit theorem also can be used to approximate probabilities for some discrete random variables when the exact probabilities are tedious to calculate. One useful example involves the binomial distribution for large values of the number of trials, n. Suppose that Y has a binomial distribution with n trials and probability of success on any one trial denoted by p. How we can obtain P (Y B)?