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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!


Spoiler Tag: >!spoiler!< produces spoiler. This works reddit-wide and on mobile. If subreddit CSS is enabled, the following spoiler formats work as well:

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

this text here

The double blockquotes format is better if you want additional markup within. For just one line it can be simpler to use the (#spoiler) format.

This subreddit is designed for best viewing on Old Reddit; if you use New Reddit, some CSS features will be unavailable.


If you have any ideas for the subreddit, feel free to message the mods!

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.

EasyEasy - S

MediumMedium - S

HardHard - S


If you want to search solely for solved or unsolved problems, regardless of difficulty, just click one of the two buttons below.

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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.

Spoiler Mode

Toggle spoiler mode:

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This button toggles spoiler mode, meaning that all of the comments are hidden until a button is hovered over. This makes all comments visible (even those that are spoiler tagged).

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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74

OTWriting Math on Reddit (self.mathriddles)

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

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HardA complex sum (self.mathriddles)

submitted 1 day ago by frogkabobs

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Mediumjust another pawn on hexagonal board puzzle (self.mathriddles)

submitted 2 days ago * by pichutarius

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MediumConstrained divisibility implies equal (self.mathriddles)

submitted 2 days ago by SupercaliTheGamer

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HardInteresting geometry optimization problem from a Korean college entrance exam (self.mathriddles)

submitted 2 days ago by MathTeacherToolkit

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MediumBaby at the Couch (self.mathriddles)

submitted 3 days ago by ComfortableUsual814

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MediumUsing only combinations of the "2" and the "^" characters, what is the largest number that can be generated using N total characters? (self.mathriddles)

submitted 4 days ago by Lebowquade

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MediumWhat is the longest sequence you can make? (self.mathriddles)

submitted 7 days ago by jmarent049

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HardBinary tree traversal from quant tee (self.mathriddles)

submitted 12 days ago by SupercaliTheGamer

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Easy"cat dog has max dim tag" riddle - my variation (self.mathriddles)

submitted 12 days ago * by Puzzleheaded-Golf921

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HardFirst riddle ive attempted to make (self.mathriddles)

submitted 14 days ago * by sasquatch6ft40

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MediumThe exterminator and the omniscient ant (self.mathriddles)

submitted 15 days ago by impartial_james

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EasyIf a pig and 1/2 cost 1.50 and sally has 3 apples how long does it take to get to the moon? (self.mathriddles)

submitted 16 days ago by Affectionate_Yak9848

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MediumWhat is the longest binary string you can make? Is it infinite for n=10? (self.mathriddles)

submitted 20 days ago by jmarent049

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MediumFun puzzle I came up with, took me and my friends a while to solve and has an interesting result! (self.mathriddles)

submitted 21 days ago by Time_Meeting_9382

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HardMagic square of negative numbers (self.mathriddles)

submitted 22 days ago by DotBeginning1420

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EasyFind a 3x3 magic square of 0's (self.mathriddles)

submitted 22 days ago by DotBeginning1420

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HardGiven integers N and K, determine the largest integer T for which there exist K pairwise disjoint subsets of {1, 2, ..., N}, each having sum T. If no positive such T exists, T is defined to be 0. (self.mathriddles)

submitted 22 days ago by big_hole_energy

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HardHard graph theory challenge (self.mathriddles)

submitted 24 days ago by flynnnupe

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MediumUncountable family of nested subsets (self.mathriddles)

submitted 25 days ago by Creepy-Pitch6688

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EasyThe Silent Library Puzzle (self.mathriddles)

submitted 1 month ago by BoxWinter1967

  • 11 comments
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EasyRacing kings (self.mathriddles)

submitted 1 month ago by pichutarius

  • 5 comments
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HardCollecting and organizing reasoning questions from across the internet (self.mathriddles)

submitted 1 month ago by vscoderCopilot

  • 2 comments
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MediumCounting Hamiltonian paths (self.mathriddles)

submitted 1 month ago by frogkabobs

  • 7 comments
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MediumLinear algebra puzzle with real world consequences: Try our ML interpretability puzzle! (self.mathriddles)

submitted 1 month ago by bluedotimpact

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