[ILUG] impressive... [OT - lotto odds]

[Aidan Keady]

> On Thu, Oct 28, 1999 at 08:59:44AM -0500, John_White at dell.com mentioned:
> > as easy as it would be to write one that gets the factorial of 5 :)
> > but you'd need a mad data type to store the result in . . .
> 
>  That's part of the point! Lisp doesn't mind!
> 
>  Question though. I was doing the lotto calculation, and:
> 
> ==> (/ (factorial 42) (factorial 36))
> 3776965920
> 
>  Is it really a 3.777 billion to one chance of winning now ?
> 
>     42*41*40*39*38*37=3776965920
> 
> Kate

No, you've forgotten the 6! in the bottom line.

i.e.  n
       C	= n!/[r!(n-r)!]
       	r

The odds against having the six numbers are only about 5.25 million to 1.

ATB,
Aidan.