The problem is to find that how many people must be there in a room for having same birthday.Than what is paradox in it? Paradox is that you may think that the possibility will only come when there are many (lets say 365) people in the room. But you shall, see this that probability shall occur even for few people.To solve this problem we index the total number of the people in the room as 1,2,3….k where k is equal to the total number of people in room.And also let us assume that all years has 365 days (ignoring the issue of leap years). Lets consider n=365 daysFor given value of i=1,2,3,…,klet bi be the day on which the birthday of the ith person is going to be celebrated, assuming 1< bi