Given twenty-four people in a room, what is the probability that there are at least two people present who have the same birthday (i.e., day and month of birth)? What is the expected number of pairs of people with the same birthday? Which of these two questions is easiest to solve? Which answer gives most insight? You may find it helpful to solve these problems and those that follow using notation such as A = number of days in year = 365 and S = number of people = 24.