# Buzzles **URL:** https://forum.beeminder.com/c/buzzles/49.md [Latest](https://forum.beeminder.com/latest.md) · [Categories](https://forum.beeminder.com/categories.md) --- ## [About the Buzzles category](https://forum.beeminder.com/t/about-the-buzzles-category/5217)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 0
Puzzles, brainteasers, math nerdery, other kinds of nerdery! --- ## [Matching Game Perfect Play](https://forum.beeminder.com/t/matching-game-perfect-play/10346)
**Author:** [@narthur](https://forum.beeminder.com/u/narthur)\ **Replies:** 38\ **Last updated:** [June 9, 2026, 10:07pm UTC](https://forum.beeminder.com/t/matching-game-perfect-play/10346 "2026-06-09T22:07:42Z")
Simplified problem statement Consider the single-player version of Memory, where you try to uncover matching pairs of cards by flipping over two at a time. If they match, remove them – if not, put them back. And assume y… --- ## [Speed Discrepancy](https://forum.beeminder.com/t/speed-discrepancy/12568)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 7\ **Last updated:** [March 26, 2026, 6:42am UTC](https://forum.beeminder.com/t/speed-discrepancy/12568 "2026-03-26T06:42:46Z")
Imagine that you biked 100 miles at an average speed of 29 miles per hour (max instantaneous speed: 40mph). Naturally you want to know if that’s a world record. Well, no one cares about imperial units \[citation needed\] b… --- ## [Turning Greek Yogurt Into Junk Food](https://forum.beeminder.com/t/turning-greek-yogurt-into-junk-food/12184)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 8\ **Last updated:** [January 29, 2025, 5:11am UTC](https://forum.beeminder.com/t/turning-greek-yogurt-into-junk-food/12184 "2025-01-29T05:11:45Z")
Here’s a puzzle for normal people. Nothing but algebra required. Also it’s super practical! We’re going to figure out how much brown sugar you can add to Greek yogurt before you’ve basically turned it into junk food. Su… --- ## [Bit-Probing The Secret List, or Cantor vs Kronecker](https://forum.beeminder.com/t/bit-probing-the-secret-list-or-cantor-vs-kronecker/12152)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 28\ **Last updated:** [January 21, 2025, 7:35pm UTC](https://forum.beeminder.com/t/bit-probing-the-secret-list-or-cantor-vs-kronecker/12152 "2025-01-21T19:35:03Z")
There’s a secret list of n+1 binary strings, not necessarily unique, each with n bits. Your mission is to name a string guaranteed NOT on the secret list, by querying as few of the n(n+1) bits as possible. This is clearl… --- ## [Followup to the Stupidly Hard Dog Logic Puzzle](https://forum.beeminder.com/t/followup-to-the-stupidly-hard-dog-logic-puzzle/5590)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 2\ **Last updated:** [August 7, 2019, 4:14am UTC](https://forum.beeminder.com/t/followup-to-the-stupidly-hard-dog-logic-puzzle/5590 "2019-08-07T04:14:37Z")
Recall our previous logic puzzle (which was the so-called Hardest Logic Puzzle Ever in disguise), about finding the identities of 3 dogs – one that always lies, one that always truths, and one that’s random – with 3 ques… --- ## [Birthdays in April](https://forum.beeminder.com/t/birthdays-in-april/11623)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 6\ **Last updated:** [June 8, 2024, 10:12pm UTC](https://forum.beeminder.com/t/birthdays-in-april/11623 "2024-06-08T22:12:04Z")
Here’s a problem that came up “naturally” on our family email list and that @bee and I have been having fun with: How many people do you have to know before probably every day in April is someone-you-know’s birthday? B… --- ## [The Inclusion-Exclusion Principle](https://forum.beeminder.com/t/the-inclusion-exclusion-principle/11612)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 3\ **Last updated:** [May 26, 2024, 7:13pm UTC](https://forum.beeminder.com/t/the-inclusion-exclusion-principle/11612 "2024-05-26T19:13:40Z")
This isn’t a puzzle but I needed to get my head around this for other puzzle-related purposes and ended up writing a little essay that I think does a nice job of making the inclusion-exclusion principle more intuitive (a… --- ## [🦜 Parrots](https://forum.beeminder.com/t/parrots/10945)
**Author:** [@april](https://forum.beeminder.com/u/april)\ **Replies:** 10\ **Last updated:** [December 17, 2023, 10:34pm UTC](https://forum.beeminder.com/t/parrots/10945 "2023-12-17T22:34:17Z")
Intro One of my favorite competitive programming tasks (IOI 2011). You don’t have to actually write any code — just come up with a way to do the task. Suitable for a) people familiar with binary, or b) programmers, or c)… --- ## [neal.fun's password game](https://forum.beeminder.com/t/neal-funs-password-game/11051)
**Author:** [@enbee](https://forum.beeminder.com/u/enbee)\ **Replies:** 0\ **Last updated:** [July 22, 2023, 12:54am UTC](https://forum.beeminder.com/t/neal-funs-password-game/11051 "2023-07-22T00:54:46Z")
now that i have completed it, i simply need a thread for it :p a truly amazing, time-consuming, infuriating, exciting, increasingly difficult puzzle game! (imo) in order to finish it, i needed: around different ta… --- ## [A Stupidly Hard Dog Logic Puzzle](https://forum.beeminder.com/t/a-stupidly-hard-dog-logic-puzzle/5252)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 25\ **Last updated:** [March 6, 2023, 12:56am UTC](https://forum.beeminder.com/t/a-stupidly-hard-dog-logic-puzzle/5252 "2023-03-06T00:56:47Z")
You encounter 3 magical dogs. One always tells the truth, one always lies, and one is Random. Whenever Random is asked a question, it flips a coin in its head to decide whether to be a liar or a truth-teller. (This is di… --- ## [Computing the Odds Ratio from sensitivity and specificity?](https://forum.beeminder.com/t/computing-the-odds-ratio-from-sensitivity-and-specificity/10552)
**Author:** [@clivemeister](https://forum.beeminder.com/u/clivemeister)\ **Replies:** 4\ **Last updated:** [September 30, 2022, 3:02pm UTC](https://forum.beeminder.com/t/computing-the-odds-ratio-from-sensitivity-and-specificity/10552 "2022-09-30T15:02:39Z")
I’ve been trying to get better at everyday-Bayesianism, by which I mean holding my current probabilities of events in the back of my mind, and updating them when new evidence appears. This is most easily done (for me) b… --- ## [Knight Transposition Puzzle](https://forum.beeminder.com/t/knight-transposition-puzzle/10433)
**Author:** [@rperce](https://forum.beeminder.com/u/rperce)\ **Replies:** 7\ **Last updated:** [July 11, 2022, 4:25pm UTC](https://forum.beeminder.com/t/knight-transposition-puzzle/10433 "2022-07-11T16:25:28Z")
A friend sent me this puzzle, and it was a neat little solution! I shared it with the community discord, and then @dreev encouraged me to post it here. Enjoy! --- ## [How long is the banana?](https://forum.beeminder.com/t/how-long-is-the-banana/10333)
**Author:** [@alys](https://forum.beeminder.com/u/alys)\ **Replies:** 5\ **Last updated:** [May 15, 2022, 7:22pm UTC](https://forum.beeminder.com/t/how-long-is-the-banana/10333 "2022-05-15T19:22:21Z")
Found at The Universe of Discourse : How long is the banana? where there is a program that determines the solution. A rope over the top of a fence has the same length on each side and weighs one-third of a pound per fo… --- ## [Blue-Eyed Monks: The Fiendish Followup](https://forum.beeminder.com/t/blue-eyed-monks-the-fiendish-followup/7520)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 18\ **Last updated:** [January 4, 2021, 12:16pm UTC](https://forum.beeminder.com/t/blue-eyed-monks-the-fiendish-followup/7520 "2021-01-04T12:16:07Z")
Recall the classic blue-eyed monks puzzle and its solution. Here is the long-awaited Fiendish Followup. You think you understand blue-eyed monks. Let me disabuse you of that notion! Ok, it’s clear that the visitor was … --- ## [A cute - even if easy - exercise in metric space theory](https://forum.beeminder.com/t/a-cute-even-if-easy-exercise-in-metric-space-theory/7387)
**Author:** [@mbork](https://forum.beeminder.com/u/mbork)\ **Replies:** 1\ **Last updated:** [October 18, 2020, 6:26pm UTC](https://forum.beeminder.com/t/a-cute-even-if-easy-exercise-in-metric-space-theory/7387 "2020-10-18T18:26:46Z")
Hi all! Do you mind if I just post a link to my blog post here? (If you prefer, I can paste in the whole puzzle.) Hope you like it! --- ## [The Classic Blue-Eyed Monks Puzzle](https://forum.beeminder.com/t/the-classic-blue-eyed-monks-puzzle/6994)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 11\ **Last updated:** [July 15, 2020, 2:45am UTC](https://forum.beeminder.com/t/the-classic-blue-eyed-monks-puzzle/6994 "2020-07-15T02:45:12Z")
This one is such a classic and so well-known that there’s a hilarious and delightful Slate Star Codex short story \[archive link\] about it, which I highly recommend, but only after you’ve puzzled over this puzzle… Ok, he… --- ## [Torricelli's Law: Calculus problem hidden in the last blog post](https://forum.beeminder.com/t/torricellis-law-calculus-problem-hidden-in-the-last-blog-post/5954)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 1\ **Last updated:** [May 24, 2020, 3:45am UTC](https://forum.beeminder.com/t/torricellis-law-calculus-problem-hidden-in-the-last-blog-post/5954 "2020-05-24T03:45:17Z")
I have despaired of anyone noticing it in the hovertext of the image so I’m putting it here: Torricelli’s Law says that if there’s a hole with radius r at the bottom of a vat then fluid flows out at a rate of 1/2\\tau r… --- ## [Spot-It puzzle via Adam Wolf](https://forum.beeminder.com/t/spot-it-puzzle-via-adam-wolf/6031)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 11\ **Last updated:** [November 27, 2019, 6:46pm UTC](https://forum.beeminder.com/t/spot-it-puzzle-via-adam-wolf/6031 "2019-11-27T18:46:01Z")
Let N be the set of natural numbers \\{1, ..., n\\} for a given n. We write the powerset (set of all subsets) of N as 2^N. Call a k-element subset of 2^N dobbly if each of the {k \\choose 2} pairs of subsets have exactly on… --- ## [An enigmatic sequence](https://forum.beeminder.com/t/an-enigmatic-sequence/5949)
**Author:** [@zedmango](https://forum.beeminder.com/u/zedmango)\ **Replies:** 3\ **Last updated:** [November 25, 2019, 7:20pm UTC](https://forum.beeminder.com/t/an-enigmatic-sequence/5949 "2019-11-25T19:20:33Z")
Interpret the following sequence: boo witt stag nke ouT --- ## [A Booty Division Theorem](https://forum.beeminder.com/t/a-booty-division-theorem/5492)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 13\ **Last updated:** [September 10, 2019, 10:41pm UTC](https://forum.beeminder.com/t/a-booty-division-theorem/5492 "2019-09-10T22:41:04Z")
Here’s one from a Beeminder user that I’ve made thoroughly ungooglable: You and your pirate buddy have 21 vaguely amorphous gold coins you want to divvy up. It turns out that if any one of the 21 coins is missing it’s p… --- ## [Phi's Programmer Madness Puzzle](https://forum.beeminder.com/t/phis-programmer-madness-puzzle/5695)
**Author:** [@phi](https://forum.beeminder.com/u/phi)\ **Replies:** 5\ **Last updated:** [August 25, 2019, 8:30pm UTC](https://forum.beeminder.com/t/phis-programmer-madness-puzzle/5695 "2019-08-25T20:30:28Z")
I’ll provide hints if necessary :wink: \[\]\[(!\[\]+\[\])\[+\[\]\]+(\[!\[\]\]+\[\]\[\[\]\])\[+!+\[\]+\[+\[\]\]\]+(!\[\]+\[\])\[!+\[\]+!+\[\]\]+(!!\[\]+\[\])\[+\[\]\]+(!!\[\]+\[\])\[!+\[\]+!+\[\]+!+\[\]\]+(!!\[\]+\[\])\[+!+\[\]\]\]\[(\[\]\[(!\[\]+\[\])\[+\[\]\]+(\[!\[\]\]+\[\]\[\[\]\])\[+!+\[\]+\[+\[\]\]\]+(!\[\]+\[\])\[!… --- ## [Team Treehouse + Beeminder = ❤](https://forum.beeminder.com/t/team-treehouse-beeminder/5664)
**Author:** [@spookane](https://forum.beeminder.com/u/spookane)\ **Replies:** 0\ **Last updated:** [August 16, 2019, 1:59am UTC](https://forum.beeminder.com/t/team-treehouse-beeminder/5664 "2019-08-16T01:59:12Z")
Hello! I’m not sure if this will be useful to anyone here, but for beginner programmers who have a Team Treehouse subscription, I have made a script that automatically adds all your Team Treehouse badges (achievements) … --- ## [A cheezy riddle](https://forum.beeminder.com/t/a-cheezy-riddle/5534)
**Author:** [@zedmango](https://forum.beeminder.com/u/zedmango)\ **Replies:** 1\ **Last updated:** [July 13, 2019, 10:50am UTC](https://forum.beeminder.com/t/a-cheezy-riddle/5534 "2019-07-13T10:50:19Z")
What kind of cheese is made backwards? --- ## [Greedy Sadistic Pirates](https://forum.beeminder.com/t/greedy-sadistic-pirates/5295)
**Author:** [@byorgey](https://forum.beeminder.com/u/byorgey)\ **Replies:** 15\ **Last updated:** [June 26, 2019, 8:16am UTC](https://forum.beeminder.com/t/greedy-sadistic-pirates/5295 "2019-06-26T08:16:16Z")
Similar to https://forum.beeminder.com/t/greedy-pirates/5285 but a bit more difficult — perhaps. I’m actually not sure yet what the correct answer is. A bunch of pirates have stolen a treasure chest full of gold and th… --- ## [Greedy \[Remorseful\] Pirates](https://forum.beeminder.com/t/greedy-remorseful-pirates/5285)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 14\ **Last updated:** [June 6, 2019, 5:06am UTC](https://forum.beeminder.com/t/greedy-remorseful-pirates/5285 "2019-06-06T05:06:03Z")
(I’m not making this one ungooglable but the standard version has enough differences that you’ll be wrong if you cheat! Also we’ll murder you. Don’t laugh, we’ve done it before!) A bunch of pirates have stolen a treasur… --- ## [Water Into Wine \[easy\]](https://forum.beeminder.com/t/water-into-wine-easy/5256)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 12\ **Last updated:** [May 26, 2019, 9:42pm UTC](https://forum.beeminder.com/t/water-into-wine-easy/5256 "2019-05-26T21:42:42Z")
(Ok, easy is relative but this is one that doesn’t require any advanced math nor does is it just stupidly, perhaps painfully, hard, like the dog logic one. It’s still tricky and clever.) You have a glass of wine and gla… --- ## [How many figure-8's can you fit in the plane?](https://forum.beeminder.com/t/how-many-figure-8s-can-you-fit-in-the-plane/5219)
**Author:** [@dreev](https://forum.beeminder.com/u/dreev)\ **Replies:** 20\ **Last updated:** [April 25, 2019, 7:04pm UTC](https://forum.beeminder.com/t/how-many-figure-8s-can-you-fit-in-the-plane/5219 "2019-04-25T19:04:58Z")
(This puzzle is from Stan Wagon via @mary’s PhD advisor and requires some knowledge of transfinite set theory which is the funnest thing and if you don’t know where to begin with this problem we can instead talk about wh… --- ## [What's the sharpe for the SPY year to date?](https://forum.beeminder.com/t/whats-the-sharpe-for-the-spy-year-to-date/5265)
**Author:** [@eugeniobruno](https://forum.beeminder.com/u/eugeniobruno)\ **Replies:** 3\ **Last updated:** [April 25, 2019, 7:24pm UTC](https://forum.beeminder.com/t/whats-the-sharpe-for-the-spy-year-to-date/5265 "2019-04-25T19:24:42Z")
Just passing along from a twitter puzzle: What’s the sharpe for the SPY year to date? Bonus: does your portfolio have a sharpe as high? :smiley: Maybe there’s some quant in here stealth beeminding? Who knows. Disclaim…