# Who are two celebrities that share the same birthday?

I bet there are millions more out there who share the same, but for two that I know, it's Chris Rock and Ashton Kutcher on February 7.

### How many people are needed in a room before two of them share the same birthday?

For the chance to be at least 50% that two people share the same birthday, there needs to be 22 people. For the chance to be exactly 100% that two people share the same birthday, there needs to be 366 people. If there was 365 people, there would be a very small chance that each person in the room would have different birthdays. With 366 people, there are not enough individual days for every person…

### What is the smallest number of people in a room where the probability of two of them having the same birthday is at least 50 percent?

23. The probability that at least two people in a room share a birthday can be expressed more simply, mathematically, as 1 minus the probability that nobody in the room shares a birthday. Imagine a fairly simple example of a room with only three people. The probability that any two share a birthday is : 1 - [ 365/365 x 364/365 x 363/365] i.e. 1-P(none of them share a birthday) =1 - [ (365x364x363) /…

### What is the probability that 25 people dont share the same birthday?

The probability that 25 random people don't ALL share the same birthday is: 1 - (1/365)**24, or about 0.999999999999999999999999999999999999999999999999999999999999968 However, I suspect you meant to ask "What is the probability that 25 random people all have different birthdays?" That is: 1 * (364/365) * (363/365) * (362/365) * ... * (342/365) * (341/365) = 0.4313 So about 43% of the time nobody will share a birthday, and 57% of the time, two or more people…

### What is the probability that two people selected from 30 have the same birthday?

To select the first birthday, the probability is 1/30. Having gotten that, the conditional probability that the next birthday would be the same is (1/30)x(1/29) and that is 1/870 ---------------------------------------------------------------------------------------------- I believe the question has to be rephrased to "What is the probability that two people in a group of 30 people share the same birthday?". Because in the way the question is actually stated, "the probability that two persons selected randomly from a group…