If you're a fan of clever bar bets and want to  make some  easy  money, you might want to try this one: The first thing is to note for  your mark (or sucker) that there are 366 possible birthdays, one for each calendar date and an extra one for leap years. Each person on Earth is going to […]

 

If you're a fan of clever bar bets and want to  make some  easy  money, you might want to try this one:

The first thing is to note for  your mark (or sucker) that there are 366 possible birthdays, one for each calendar date and an extra one for leap years. Each person on Earth is going to have a birthday on one of those 366 dates.

Now, tell your mark that he or she can choose any 57 people at random, and you're willing to bet any amount of money that at least two of those people share the same birthday.

The names can be chosen at random from the rolls of Congress or the  state legislature  or NFL rosters or whatever.   The only requirement is that the names be chosen randomly. And you'll need some source that lists the birth dates of the people who have been selected.

Anyway, in 99 cases out of 100, you're going to win the bet.

How can this be?  With 366 possible birthdays, how can it be almost a lead-pipe cinch that there'll be a duplicate birthday among just 57 randomly-selected people?

I don't know how.   But that's the way it works. It has something to do with the laws of probability.

Moreover, there's a 90-percent chance  of a duplicate birthday among just  41 randomly-selected people. And there's a  50-50 chance among just  23 people.

Now, of course, if you win any bets on this thing, I'll expect my customary 10 percent commission.