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What is the maths name for a "washer" - a circle with another smaller concentric circle removed? It is a sort of 2D torus. -- SGBailey ( talk) 09:06, 28 October 2015 (UTC)
The Annulus (mathematics) article says that the figure is equivalent to a punctured plane, and links to Glossary of topology. I thought I'd qualify the link to point to the correct entry, but there is none with that name. The closest appears to be "punctured neighbourhood". Is that the same concept? Rojomoke ( talk) 12:55, 28 October 2015 (UTC)
I assumed this question had been canvassed before, but I couldn't find it in the Archives.
I know there's a fairly easily obtained exact answer to the question of how many possible
chess games there can be. There's possibly a reasonably exact answer for the same question about
Scrabble, but it seems the only way to be sure is to enumerate them all, and that would take far, far longer than the age of the universe, so it's not terribly what you might call practical.
However, surely we can at least come up with an upper bound.
Can we come up with an upper bound for the number of possible Scrabble games?
This says there are 5.716 × 10^300 possible valid Scrabble configurations.
But this gives the much lower figure of 69 × 10^180, and then excludes an unnamed proportion of them as being invalid, so it works out even lower.
These two results inhabit ball parks that are not even in the same galaxy, let alone the same city. Can anyone comment on them, and suggest the true value? Thanks. -- Jack of Oz [pleasantries] 21:26, 28 October 2015 (UTC)
Mathematics desk | ||
---|---|---|
< October 27 | << Sep | October | Nov >> | October 29 > |
Welcome to the Wikipedia Mathematics Reference Desk Archives |
---|
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
What is the maths name for a "washer" - a circle with another smaller concentric circle removed? It is a sort of 2D torus. -- SGBailey ( talk) 09:06, 28 October 2015 (UTC)
The Annulus (mathematics) article says that the figure is equivalent to a punctured plane, and links to Glossary of topology. I thought I'd qualify the link to point to the correct entry, but there is none with that name. The closest appears to be "punctured neighbourhood". Is that the same concept? Rojomoke ( talk) 12:55, 28 October 2015 (UTC)
I assumed this question had been canvassed before, but I couldn't find it in the Archives.
I know there's a fairly easily obtained exact answer to the question of how many possible
chess games there can be. There's possibly a reasonably exact answer for the same question about
Scrabble, but it seems the only way to be sure is to enumerate them all, and that would take far, far longer than the age of the universe, so it's not terribly what you might call practical.
However, surely we can at least come up with an upper bound.
Can we come up with an upper bound for the number of possible Scrabble games?
This says there are 5.716 × 10^300 possible valid Scrabble configurations.
But this gives the much lower figure of 69 × 10^180, and then excludes an unnamed proportion of them as being invalid, so it works out even lower.
These two results inhabit ball parks that are not even in the same galaxy, let alone the same city. Can anyone comment on them, and suggest the true value? Thanks. -- Jack of Oz [pleasantries] 21:26, 28 October 2015 (UTC)