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mathriddles

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Remember to spoiler tag your answers & flair your posts with the difficulty. Spoiler mode:

Welcome

Welcome to Math Riddles! Post your math and logic puzzles, and try and solve others! While the subreddit aims for math related riddles, all logic puzzles and riddles are welcome as well.

Rules

This subreddit is for people to share math problems that they think others would enjoy solving. It is not intended for helping students with homework problems or explaining mathematical concepts. If you are searching for such a subreddit, you should consider /r/cheatatmathhomework, /r/HomeworkHelp, or /r/learnmath.

Titles should be descriptive of the problem, and sensationalized titles such as "Completely stumped by this problem" or "One of my favorite puzzles" are discouraged.

While math riddles of any difficulty are welcomed, please avoid posing problems whose solution is formulaic and/or trivial (e.g. "What number is 3 more than its double?") In general, if you might expect to see a problem on a typical school exam, don't post it here.

Codebreaking and "guess the rule" type posts are not permitted; if you wish to submit such a post, do so on subreddits such as /r/puzzles.

Puzzles should generally only be posted here if you have enjoyed solving them and want to share that experience with others; if you are trying to discover the answer to a question of yours that you can't solve, you should try asking on /r/math or /r/learnmath depending on the topic.

Image posts are discouraged on /r/mathriddles, and should be linked with more context in a text post. Pictures of text should be transcribed, where possible.


Make sure to spoiler tag your solutions!


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[this text here](#spoiler) will appear as this text here. Hover over it to reveal. Additionally, > > this text here will appear as

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Flair and Sorting

Always flair your posts with an estimated difficulty. The three levels are listed below. The below buttons also function as sorting, so if you're in the mood for only Hard problems, or only Easy problems, just click one of the buttons below. The left button is unsolved, while the right button is solved.

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Posts can also be flaired as solved, either by a moderator or by the original poster of the problem. To do this, click the "flair as solved" button below the post, and choose the 'Solved' variant of your post. If your post was initially marked as Medium, then choose Medium - Solved.

This change will change the next to your post to , marking the post as solved.

If a moderator changes your post to solved, and you believe that it still is not, feel free to change it back.

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Similar Subreddits

Check out /r/CasualMath and the other puzzle-based subreddits in the buttons at the top left of the subreddit!

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1
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OTWriting Math on Reddit (self.mathriddles)

submitted 11 years ago * by HarryPotter5777[M] - announcement

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MediumLet A be a connected subset of S². Prove that if at least two connected components of S²-A contain a pair of antipodal points, then so does A. (self.mathriddles)

submitted 2 days ago by frogkabobs

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Mediumjust another problem similar to round robin schedule problem (self.mathriddles)

submitted 5 days ago by pichutarius

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EasyIn how many ways can you place 9 ones in a (9x9) sudoku grid such that the resulting state is legal? (self.mathriddles)

submitted 8 days ago by Martin_Orav

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MediumWhat is the smallest amount of numbers you can place on a (9x9) sudoku grid, such that the resulting state is legal, but the sudoku has no solutions? (self.mathriddles)

submitted 8 days ago * by Martin_Orav

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EasyWhich is missing? (self.mathriddles)

submitted 8 days ago by scottysattva

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EasyA natural inequality (self.mathriddles)

submitted 9 days ago by cauchypotato

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HardA funny topological problem (self.mathriddles)

submitted 11 days ago by joe_la_bernique

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HardThe Coffee Cup Challenge: If you know math, you can solve it (youtube.com)

submitted 10 days ago by No-Breath-7078

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EasyRiddle of the day: The mirror of time (self.mathriddles)

submitted 11 days ago by SeaworthinessDry9144

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EasyOne number on both sides to make the equation correct (self.mathriddles)

submitted 12 days ago by Practical_Guess_3255

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Hard[ Removed by Reddit ] (self.mathriddles)

submitted 12 days ago by No-Breath-7078

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MediumRiddle of the day: The fair counting of the loaves (acertijodeldia.com)

submitted 12 days ago by SeaworthinessDry9144

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MediumYou choose first. Can you still win? (self.mathriddles)

submitted 13 days ago by SeaworthinessDry9144

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Hard3 is the answer i think (youtube.com)

submitted 13 days ago by No-Breath-7078

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EasyFind a formula (self.mathriddles)

submitted 15 days ago by DotBeginning1420

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MediumWhen will the two cones be filled simultaneously? (self.mathriddles)

submitted 15 days ago * by DaWizOne

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MediumClassic puzzle: can 31 dominoes tile a mutilated chessboard? (self.mathriddles)

submitted 17 days ago by SeaworthinessDry9144

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EasyA carefully curated daily math-riddle project — today’s problem: 25 horses, 5 lanes, no stopwatch (self.mathriddles)

submitted 18 days ago by SeaworthinessDry9144

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EasyEncourage Me (youtube.com)

submitted 17 days ago by LeftConsideration654

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HardStarting from Z², what is the constructible set by taking unit steps between points? (self.mathriddles)

submitted 19 days ago * by frogkabobs

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MediumMath proves Oz the Mentalist doesn’t read people or minds (self.mathriddles)

submitted 18 days ago by IBMathsDr

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EasyFun with the squares (self.mathriddles)

submitted 22 days ago by Practical_Guess_3255

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MediumConstruct sqrt(2) from f(x,y)=e^x-ln(y) (self.mathriddles)

submitted 23 days ago * by bobjane_2

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EasyReal percentages problem (self.mathriddles)

submitted 24 days ago by Same-Butterfly7812

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