Another brain stretcher

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Deleted member 21081

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How many people would you need in a room before the probability of 2 of them sharing the same birthday becomes likely?

Again please answer and I’ll private message you so as not to spoil it for others.
 

Neil ofthe nene

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I know that it is a high probability with 30 or more. But I don't know the exact number.
 

PAB

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with around 23 people there's a 50-50 chance and with 75 there's over 99% chance I recon. it was a old question we always had to work out at school.
 

Spadger123

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Maths makes my head hurt. At a guess and I haven't googled it I would say about 70-80 but that does not take into account the leap year factor.
 

spanky

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A rough look at permutations suggests 20 (190 permutations, just over half of 365) ... certainly when I simulated with 35 I got a lot more instance with matching dates than not and 20 seems to work.
 
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