# Thread: Likelihood

1. ## Likelihood

Hi!

If there are 10 people in the same room and they were all born in the same year what would be the likelihood that at least two of them were born exactly the same day?

Please help me with that one

2. Originally Posted by Shandy
Hi!

If there are 10 people in the same room and they were all born in the same year what would be the likelihood that at least two of them were born exactly the same day?

Please help me with that one
The probability is 1 - the probability of them all being born on different days.

$p = 1 - \frac{365!}{365^{10}(365-10)!}$

$p = 1 - \frac{365\times 364\times 363\times 363 \ldots 356}{365^{10}}$

$p \approx 0.1169481777$

3. Originally Posted by Shandy
Hi!

If there are 10 people in the same room and they were all born in the same year what would be the likelihood that at least two of them were born exactly the same day?

Please help me with that one
Read this: Birthday problem - Wikipedia, the free encyclopedia

4. Originally Posted by mr fantastic
If I recall correctly, there is also a nice discussion of the problem in the short Arthur C Clarke novel A Fall of Moondust.