In Happy Birthday, the question was if there are N people in a room, what is the probability that there are at least two people in the room who share a birthday?

What if instead exactly two was required? If there are N people in a room, what is the probability that there are exactly two people in the room who share a birthday?

(Note: Assume leap year doesn't exist, and the birthdays are randomly distributed throughout the year.)

The probability that the first two have the same birthday,  but the rest do not match any of the others is

Edited on September 22, 2023, 10:22 pm

Posted by K Sengupta on 2023-09-22 09:15:49