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Topic:
why do buses always come in 3s? , math book?
Replies:
69
Last Post:
Jun 19, 2000 2:26 AM




Re: why do buses always come in 3s? , math book?
Posted:
May 27, 2000 12:06 PM


prezky@apple.com says... > Don McDonald <dsmc@actrix.gen.nz> wrote:
[Mean lowest number in a 40choose6 lotto game]
> > > = 41/7 > > > > =?? (N+1) / (L+1). ?? > > is this correct.? [snip] > > possible argument about beads on a necklace. > Yes, how does it go again?
Isn't it something like this:
The N numbers represent gaps between N+1 beads on a string. Choosing L numbers from N without replacement corresponds onetoone to choosing a way of colouring the N+1 beads with L+1 colours, with at least one bead of each colour (since without replacement), and then stringing them on the string so that colours are contiguous and in a particular order. (The gap between two beads of different colours represents a lotto number.) The mean value of the lowest number equals the mean number of beads of the first colour (or any colour), and that's easy to work out.
Have I got that right?
James Lawry.



