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June 23, 2008 7:11 AM   Subscribe

I need some mind-bendingly difficult brain teasers.

I used to tackle these all the time back in high school, and my passion for them was recently rejeuvenated when I picked up Professor Layton for the Nintendo DS. I've been searching online, but all I come across are sites with crappy little riddles and math problems. I need some big guns. If you have any really great ones or know of a site that catalogues a trove of them, please post them here.
posted by Christ, what an asshole to Grab Bag (16 answers total) 47 users marked this as a favorite
posted by Jaltcoh at 7:46 AM on June 23, 2008

I've always been a fan of Nick's Math Puzzles (and by "a fan of" I mean "deliciously frustrated by".)
posted by Johnny Assay at 7:54 AM on June 23, 2008

Also, if you want ridiculously difficult math problems, try the Putnam problem archive.
posted by Johnny Assay at 7:59 AM on June 23, 2008

Also, Newcomb's Problem.
posted by Jaltcoh at 8:14 AM on June 23, 2008

IBM's Ponder This (most of these also fall into the "difficult math problems" category)
posted by DevilsAdvocate at 8:37 AM on June 23, 2008

This had me and several of my friends swearing for several days:

The World's Hardest Easy Geometry Problem

I sketched it out in crayon on the paper tablecloth where we were eating, which lead to a rapid proliferation of triangles across the table.

I gave up; there's apparently a solution, although I won't link to it, since that would spoil the fun...
posted by kothar at 9:11 AM on June 23, 2008

If you're into logic puzzles take a few LSAT questions and feel sorry for all the law students.
posted by martini at 9:47 AM on June 23, 2008

Response by poster: Does anyone have more story-related ones? The math ones require more pencil-paper treatment. I'd like ones my friends and I can hawk over during a cocktail party.
posted by Christ, what an asshole at 10:55 AM on June 23, 2008

You might dig these lateral thinking puzzles.
posted by Hlewagast at 11:00 AM on June 23, 2008

Another earlier thread.
posted by Gyan at 1:02 PM on June 23, 2008

It's funny... I just did a search for a puzzle I solved, and forgot about ("The Bridge"). And found it (and more) here. Currently stuck on "Alphabet Blocks".
posted by ObscureReferenceMan at 1:20 PM on June 23, 2008

If you like logic puzzles I cannot recommend Raymond Smullyan's books more -- What's the Name of this Book? and Alice in Puzzleland. They can be hard to find since they don't seem to be in print anymore but I worked through all the puzzles as a teenager and found them really mind-bending.
posted by peacheater at 2:13 PM on June 23, 2008

The MIT Mystery Hunt has really hard problems and they're online. Not so many stories though... stories make them too easy.
posted by smackfu at 7:39 AM on June 24, 2008

These three have an underlying mathematical foundation to them, but also can be solved using an intuitive process as well. I've found that the chicken mcnugget one is especially good with kids and computer scientists.

Chicken McNuggets come in sizes 6, 9, and 20. What is the largest number of McNuggets that they cannot serve you? For example, they can serve you 26 (a 20 pack and a 6 pack) but not 25. (Or is there a largest number?)

Suppose you have a coin that may or may not be 50-50 chance of heads and tails. What can you do to still use the coin and make it 50-50?

Suppose you have a pile of small chips (randomly distributed) and a bunch of ants on a flat surface. The ants run around randomly. If an ant runs into a chip and is not carrying anything, it will pick up that chip and then continue to move about randomly. If an ant, on the other hand, is already carrying a chip and runs into another chip, it will drop the chip it is carrying and then continue to move about randomly. What does the surface look like after a long period of time? That is, how are the chips distributed?

Also, a collection of brain teasers / math puzzles:
posted by jasonhong at 7:28 PM on June 24, 2008

Sorry to necro such an old thread, but I came across it when browsing the archives and I wanted to recommend Foggy Brume's P&A Magazine. The puzzles are fantastic. He also created a free really cool online puzzle extravaganza called The Puzzle Boat.
posted by painquale at 3:17 AM on August 8, 2008

Here's a couple:

A perfect number is a positive integer which is the sum of its positive divisors. For example, 14 + 7 + 4 + 2 + 1 = 28, so 28 is a perfect number. Can you find an odd perfect number? If not, why not?

Show that every even integer greater than 2 can be written as the sum of two primes.

(Make sure to MeMail me the answers if you get 'em!)
posted by grobstein at 4:22 PM on April 3, 2009 [1 favorite]

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