
Ask HN: The Birthday Problem - ryanthedev
What&#x27;s the probability of two people sharing the exact birthday? (dd-mm-yyyy)
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wallflower
It is similar to the problem of grocery checkout. If there are n checkout
lines, the probability of being in the quickest line is 1/n, assuming that all
checkouts have lines.

It is probably 1/(how many possible birthdays in a given year range). To be
conservative (90 years): 1/90*365 or 0.003%.

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ryanthedev
Is 90 years the representation of the average age of a person?

What if it didn't matter that they were alive or dead?

Meaning I have a hat with every name and birthday of every "human". Every time
someone is born, their name is added to the hat. Essentially an infinite set
of names would be added.

What's the probability when N is infinite? Like a grocery store with an
infinite amount of checkout lines.

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pwg
1) Open browser

2) Navigate to [https://duckduckgo.com/](https://duckduckgo.com/)

3) Type in "!w birthday problem" (without the quotes)

4) Read the wikipedia page that appears

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ryanthedev
Thanks! I scoured the wiki. Didn't find any examples of using an infinite set.
Could you be a bit more specific? It's definitely possible I missed the
section.

