Coin rotation paradox: This term has been used in a popular internet video and in few books which rather target maths learners than scientific demands.  But since it isn't really a paradox and covered by regular geometry, this doesn't need an article for it's own.
 Is is correct that there was an mistake in the exam, but this was not really because of a phenomen called "coin rotation paradoxon" then, this was just because of a wrong calculation.  In the linked youtube video it was goven the name "paradoxon" and given an extra-complicated explanation to make a paradoxon out of a simple calculation.
 See also discussion page for more.  - Flexman ( talk ) 01:33, 27 December 2023 (UTC) [ reply ] Automated comment: This AfD was not correctly transcluded to the log ( step 3 ).   I have transcluded it to Wikipedia:Articles for deletion/Log/2023 December 27 .   — cyberbot I Talk to my owner :Online 01:48, 27 December 2023 (UTC) [ reply ] Note:  This discussion has been included in the list of Mathematics-related deletion discussions .  Shellwood ( talk ) 02:20, 27 December 2023 (UTC) [ reply ] Keep - There are (as far as I can tell) two arguments presented in favor of deletion: It's "not a paradox" and it's redundant to some as-yet unidentified article.  This particular quirk of rotations is not discussed at geometry , nor was I able to find it after a brief skim of rotation (geometry) , so presumably the nominator was thinking of another article, but until that article is specified, this argument is incomplete.  As for "not a paradox" - take it to WP:RM .  Badly-titled articles should not be deleted, they should be renamed.  -- N Y Kevin 02:36, 27 December 2023 (UTC) [ reply ] Maybe it fits into the article of rotation.  This video provides the simple answer without calling it paradox: If the radius of circla A is 1/n of the radios circle B, the answer is n+1.  Nothing paradox about it.  There isn't even an expression for "Coin rotation paradox" in other languages since it is more connected to the phenomen of this SAT test than to regular science.  Flexman ( talk ) 10:52, 27 December 2023 (UTC) [ reply ] It is indeed a veridical paradox .  The coin rotates more when rolling around another coin than when rolling on a line segment of the length of the latter coin's circumference.  This is strongly counterintuitive at the first glance, enough to be called a paradox.  If this wasn't a paradox, just geometry , birthday paradox would also not be a paradox, just simple probability calculations.  Janhrach ( talk ) 21:14, 30 December 2023 (UTC) [ reply ] Keep There are plenty of sources for this, the article should be cleaned up for sure but it passes WP:GNG Dr vulpes (Talk) 05:21, 27 December 2023 (UTC) [ reply ] Murtagh, Jack.  "The SAT Problem That Everybody Got Wrong" .  Scientific American .  Retrieved 2023-12-27 .  Keep : Seems to pass GNG.  For the record, I contested the PROD.  Queen of Hearts ❤️ (she/they 🎄 🏳️‍⚧️) 07:55, 27 December 2023 (UTC) [ reply ] There's a tendency of certain people on YouTube to call everything a "paradox" as clickbait.   This is one of the reasons that YouTube isn't a very good source.   But the right answer, if it is a documented mathematics topic, is to take the YouTube clickbait out of the title, not nominate the article for deletion.  Uncle G ( talk ) 13:20, 27 December 2023 (UTC) [ reply ] Comment "Paradox" is definitely sensationalistic; "puzzle" would be justifiable, as it appears in books of them, e.g., [43] [44] .  An abstracted version of the puzzle appears in group theory [45] .  XOR'easter ( talk ) 15:48, 27 December 2023 (UTC) [ reply ] Agree with XOR'easter that calling it [a?] coin rotation puzzle rather than paradox would be more apt.   -- JBL ( talk ) 18:51, 27 December 2023 (UTC) [ reply ] If we take a look on Deferent and epicycle , does this have a relation to the puzzle?  - Flexman ( talk ) 23:20, 29 December 2023 (UTC) [ reply ] Vaguely but not even really enough to be worth mentioning in either article.  — David Eppstein ( talk ) 07:21, 31 December 2023 (UTC) [ reply ] You won't be shocked to know that Gardner did an extension to a single coin rolling around a closed loop of n coins ( n > 2 ) in Mathematical Carnival in 1975, which was an updated version of xyr 1966 Scientific American column.   And the chapter in the book is titled "Penny Puzzles".  Uncle G ( talk ) 19:44, 27 December 2023 (UTC) [ reply ] Strong keep : It is too specific a phenomenon to belong to geometry or similar articles.  Just because it is obvious to Flexman doesn't mean it is to others; it is described in Scientific American , Wolfram MathWorld etc.  Regarding the name, a Google search shows many parties calling it a paradox .  cmɢʟee ⎆ τaʟκ 03:24, 28 December 2023 (UTC) [ reply ] MathWorld is known to be a bad source for terminology, and a generic Google search turns up unreliable rubbish.  XOR'easter ( talk ) 15:53, 28 December 2023 (UTC) [ reply ] Also the choice of title of the Wikipedia article for a relatively obscure thing like this with no "real" name will have a pretty big impact on the google hits.  100.36.106.199 ( talk ) 01:48, 29 December 2023 (UTC) [ reply ] Keep: “This isn't even a paradox, it's just geometry” is such a lame excuse for destroying someone’s hard work on writing an article on a truly remarkable topic (in geometry :-p) that has garnered significant attention in both popular and scholarly circles.  It’s extremely telling that you would rush immediately to deleting it instead of first suggesting a rename or something non-destructive.  Stop the deletionism!  — Timwi ( talk ) 10:42, 28 December 2023 (UTC) [ reply ] Keep The notability of this mathematical phenomenon does not seem to be in dispute.  Maybe the title should be changed, but I would note that describing counter-intuitive results as paradoxes is very much a regular occurrence in the field.  TompaDompa ( talk ) 19:09, 28 December 2023 (UTC) [ reply ] Keep : discussed in many reliable sources, clearly notable.  Deleting this article solely because it uses the term "paradox" in a colloquial sense is absurd.  Must we also then delete Epimenides paradox , Barbershop paradox , Cantor's paradox , and every other non-intuitive but logically sound idea?  Dan • ✉ 04:53, 30 December 2023 (UTC) [ reply ] Keep : This seems like a clearly notable observation/phenomenon.  Retitling would be fine if someone can find a different name which is more common (or comparably common and clearer).  – jacobolus (t) 05:55, 30 December 2023 (UTC) [ reply ] Keep .  There are plenty of sources.  As nominated, it already had two sources associating it with a "paradox" (Mathworld and Mathematical Fallacies and Paradoxes ) and a major national newspaper story about the SAT snafu.  There is plenty more where that came from; for instance Martin Gardner also calls it the "coin paradox" (again separate from the SAT).  There is no need to rename; it fits perfectly well into Category:Mathematical paradoxes which clearly states on the category page "Paradox" here has the sense of "unintuitive result", rather than "apparent contradiction".  The fact that this is unintuitive is attested by the failure of the SAT creators to notice the problem and the tiny percentage of SAT participants who reported the problem.  — David Eppstein ( talk ) 06:16, 30 December 2023 (UTC) [ reply ] The above discussion is preserved as an archive of the debate.  Please do not modify it.  Subsequent comments should be made on the appropriate discussion page (such as the article's talk page or in a deletion review ).  No further edits should be made to this page.

Discussion outcome: keep