Another brain stretcher

[Deleted member 21081]

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]

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

 

[PAB]

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]

2 if they are twins

 

[DFL]

It’s my birthday tomorrow, I’ll have a look.

 

[Deleted member 21081]

2 if they are twins

Not a trick question.

 

[Spadger123]

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]

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.