1. The problem statement, all variables and given/known data Suppose that, on average, 70% of graduating students want 2 guest tickets for a graduation ceremony, 20% want 1 guest ticket and the remaining10% don't want any guest tickets. (a) Let X be the number of tickets required by a randomly chosen student. Find the mean and variance of X. (b) If 500 guest tickets are available for a ceremony at which 300 students are graduating, what is the probability that there will not be enough tickets to satisfy demand? 2. Relevant equations Variance = E(X2) - E2(X) 3. The attempt at a solution I've got the mean to be ((0.7*2) + (0.2*1) + (0.1*0))/3 = 0.53and the variance to be ((0.72*2) + (0.22*1) + (0.12*0))/3 - 0.532 = 0.7391 but this seems wrong because the variance is then bigger than the mean?!?!?!