The birthday problem and the lottery

[Frank]

Heres a conundrum. Imagine a room full of people who chat and ask each other what is the date of their birthday. What is the minimum number of people there would need to be in the room such that the probability of two people having the same birthday was 50% ?

It a well known conundrum which leads on to lotteries and how many draws need to be out before a result repeats.

I won't tell you the answer yet and if you don't know it some of you might like to think about it . Some of you might google it anyway. (Better if you don't as its good food for the brain).


Anyway I'll be back after a while and we'll talk about how this affects lotteries.