If you take a group of people born in a non leap year you would need 366 people for a 100% chance that someone shares a birthday but only 23 people for a 50% chance that somebody shares a birthday?
In: Mathematics
– Find a 20-sided die (a D20) and start rolling it.
– Every time you roll it, write down the number.
– If you roll a number that you have already written down, stop.
If you roll it twice, it’s pretty unlikely that there’s going to be a “collision”, because you’d need to roll the same number twice in a row.
But what if you’ve rolled the die 10 times already? At that point, it’s a 50-50 shot of rolling a number that you’ve already seen. Much better odds.
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