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Questions tagged [open-ended]

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70
votes
15answers
13k views

Making π from 1 2 3 4 5 6 7 8 9

There have been two other questions here and here that are similar to this one, but this changes the rules up a little. Your job is to approximate $\pi$ using the sequence of digits (in order): 1 2 ...
59
votes
19answers
9k views

Growing anagrams - What is the longest possible list forming a sentence?

This is a challenge for word-puzzle lovers. It might be a bit more of a game than a puzzle, but I think it is not limitless in it's answers, so a final answer could be found (eventually). What is ...
43
votes
9answers
21k views

The Longest Word Made from Chemical Symbols [closed]

So, as you probably know, each and every element in the Periodic Table has its own unique chemical symbol, which is either one, two, or three letters long. For instance, Oxygen is represented as O and ...
33
votes
21answers
12k views

3:3! It's a football score! [closed]

Given to me, by a friend: How would you make 20, using two threes? You may use any basic operation. And others, such as square roots (the symbol), factorials, etc. Any operation is allowed. Just ...
28
votes
9answers
5k views

How many consecutive positive integers can you make using exactly four instances of the digit '4'?

Starting at 1 (which is 4 - $\sqrt4$ - 4/4), how many consecutive integers can you make using exactly four instances of the digit '4'? Basic rules: Any operator symbol is "free". Any printed '4' ...
28
votes
3answers
915 views

Rook River (Chess Sliding Puzzle)

The absent-minded king has gotten himself lost. Help him return to his palace on h8 using as few moves as possible. Only legal chess moves are allowed. Pawns are not promoted on the final rank. You ...
27
votes
18answers
16k views

Don't settle for a billion [duplicate]

While Artur is willing to settle for a billion, I'd like a much bigger return on my two matchstick investment. Moving only two matchsticks, what is the largest number that can be created from the ...
26
votes
7answers
11k views

The most words that can be made by successively adding one letter to the original word?

What is the largest number of words that can be made by just adding one letter to the original word, where each iteration is a meaningful word? E.g. ...
25
votes
13answers
4k views

A rhopalic sentence of at-least 5 words, beginning with as long word as possible

Rhopalic sentences are sentences which have words whose length is one more than the previous word. eg: I do not hunt birds. I do not know where family doctors acquired illegibly perplexing ...
22
votes
13answers
7k views

Playing “Guess a Number” with myself

I want to play a game where one person thinks of a number and the other tries to guess it, but I want to play this game by myself. The puzzle is to come up with a way to play this game. Rules (have ...
22
votes
9answers
3k views

Longest “De Bruijn phrase” in English

Let's call De Bruijn n-phrase a sequence $S$ of n words $W_1 W_2 W_3... W_n$ such that any "left-rotation" of its words constitutes a correct and meaningful phrase. The left-rotations of $S$ are: $...
22
votes
6answers
3k views

From Puzzling to StackExchange

This is a variation of a game I used to play with my friends in my childhood. You are given a starting word, and using the following operations, you have to reach the target word. The solution that ...
21
votes
9answers
3k views

Riddles/puzzles having answer hidden in the question? [closed]

Can you give any example of riddles or puzzles in which the answers are someway "cleverly hidden" inside the question? I think that such examples are more common in word-related riddles, but maybe ...
21
votes
9answers
2k views

Word Tank-chain-wheel Challenge

My niece gave me this word wheels challenges the other day and I comes up with an alternative. Here's how this challenge works: Find a word that can form another word by moving its first letter ...
21
votes
2answers
3k views

Open-ended challenge: Find the longest morsagram word pair

The idea for this challenge stems from this posting on ComputerScience (beta). It is established (see above link), that Morse-code requires the 'space' between individual character to be uniquely ...
20
votes
8answers
4k views

Craft the longest Scrabble sentence

This is another challenge along the same vein as similar challenges that have shown up on this site, requiring the puzzle to craft the longest possible sentence given a specific requirement. What is ...
20
votes
4answers
1k views

Strategy to beat the casino over the long haul

$A$ and $B$ are attempting to beat the casino again, and the rules are the same: Each round, $A$, $B$, and the casino simultaneously decide to show a $0$ or a $1$. If all three numbers match, $A$ ...
18
votes
26answers
11k views

Building a 2 mile runway on a 1x1 mile island [closed]

You have a 1-mile long x 1-mile wide island. When taking off from a flat runway, a plane requires a runway of minimum length 2 ...
18
votes
7answers
3k views

What is the longest rhymonym?

What is the longest pair of words you can find that rhyme and can also be synonyms / used to describe the same phenomenon? For instance, spot and ...
18
votes
4answers
3k views

A Tic-Tac-Toe type game

I found this interesting game with no name: You have a 1x11 grid, like this. The way you play is similar to Tic-Tac-Toe (aka Noughts and Crosses). Players take turns to place Xs and Os on the grid, ...
18
votes
5answers
1k views

‘‘Loopy’’ C loop

What is the smallest number of non-space characters that can be added in order to change the following code into a complete C program that prints  ...
18
votes
1answer
791 views

Peaceful Encampments

This math puzzle is due to Donald Knuth (as far as I know; maybe he got it from someone else) circa 2014. Consider a plain represented by the unit square. On this plain we want to “peacefully ...
17
votes
5answers
2k views

Second-rate spelling

Find the longest word which can be spelled with the second letters of a group words in alphabetical order. An example with incomprehensible (16 letters): a...
15
votes
8answers
6k views

Longest Word With *Only* Repeating Character Pairs

Inspired by and Opposite of: Longest Word without repeating character-pairs The challenge is to find an English word in which every character pair appears at least twice. ("Word" does not include ...
15
votes
3answers
2k views

The Sphinx's Dice

"I'm bored of riddles, I'm going to ask you a question about dice instead", says the Sphinx. "Now, I've got this set of Efron Dice here. There's four dice, and they have these values on their faces:" ...
14
votes
9answers
890 views

Interaction of the three kinds

There're three kinds of it. Any two of the same kind will give you that same kind. Any two of the different kinds will give you the remaining kind. What is it? I don't know the ...
14
votes
3answers
1k views

How many consecutive integers can you make using only four digits?

In the spirit of the classic four fours, I wonder what's the optimal set of four numbers? Your goal is to make the most consecutive integers using four digits of your choice. Pick four: $0,1,2,3,...
14
votes
3answers
369 views

Pool of Pawns (Chess Sliding Puzzle)

The King has tired of watching the Queen swim in the Pool of Pawns. Help him return to his palace on h8 using as few moves as possible. Only legal chess moves are allowed. Pawns are not promoted on ...
14
votes
3answers
607 views

Forced selfmate in n-moves

I assume most people on PSE know a bit of chess With white to move, this is checkmate (1. Qb7#): That's boring. Let's try something more interesting. With black to move, black can FORCE white to ...
13
votes
14answers
4k views

Shortest sentence with two auto-antonyms

You have to use two words that are each their own opposite (auto-antonyms, contronyms, contranyms or whatever you want to call it) in the same sentence. This means that each of the two words in used ...
13
votes
3answers
635 views

The Longest -1 Word

What is the longest -1 word (or the word worth most in Scrabble for words with the same amount of letters(which is just the addition of all the letter values of the original 'word', no constraints)), ...
13
votes
6answers
370 views

Pulling Apart a Jigsaw Puzzle

Assume you have a jigsaw puzzle that is also a tessellation. This means every piece has an identical shape and can be assembled into a 2D pattern that fills the plane with no gaps. Such a jigsaw ...
13
votes
3answers
1k views

From jafe to El-Guest

Largely inspired by From Puzzling to StackExchange by CodeNewbie From jafe to El-Guest jafe > cafe > cate > cete > cet > get > gest > egest > e gest > e guest > el guest Rules: In any move, you ...
13
votes
6answers
3k views

Can you solve those laser puzzles? (puzzles created by the community) [closed]

So, I was bored and I made a small game for this site! In this game the user who solves the previous puzzle gets to create the next one and they will always be more complex. Website link and string ...
13
votes
3answers
680 views

100 Dwarves vs. the Evil Elf

The following is an extension of 100 Dwarves and a tiny room. The text of this puzzles spoils that one in a minor way, so go read that excellent puzzle first! An evil elf puts $100$ dwarves in a ...
12
votes
18answers
22k views

Find words with the highest proportion of a single letter

Thanks to JoeZ, pacoverflow, isaacg, Sp3000, Novarg, Ram, h34, and all those who contributed answers that have since been beaten. I've accepted JoeZ's answer since he has the most mentions on the list ...
12
votes
3answers
349 views

You may remove pieces of your opponent's!

You are in a regular chess tournament, your opponent is Deepest Blue AI who considers every kind of possibilities and does not make any mistakes. But you are given an opportunity to remove any pieces ...
12
votes
3answers
525 views

Masyu puzzles with many circles

The rules of Masyu: Make a single loop with lines passing through the centers of cells, horizontally or vertically. The loop never crosses itself, branches off, or goes through the same cell ...
12
votes
2answers
528 views

KenKen Zen: A journey begins

Let us shy away from the materialistic opulence of 361- cell KenKen layouts (−9 to +9, squared).  Let us contemplate a modest KenKen journey, unburdened by gratuitously ...
11
votes
8answers
7k views

Longest sentence where all words are anagrams of each other

Won, now own. Rules: A “word” is an entry on dictionary.com. A “sentence” is any text that is grammatically correct, has a complete meaning in the English language, starts with a capital letter and ...
11
votes
11answers
4k views

Longest sentence with each letter repeated n times

Inspiration: This question was inspired by Word sets with no repeating letters Rules: Sentences can be of any length. Every letter used in this sentence, must be used n times. n can be any number. ...
11
votes
7answers
3k views

Longest arithmetic expression where the answer is equal to the number of letters

You can use any mathematical operations represented by English words. These English words must be found in a commonly used dictionary. Spaces are neither letters nor words. You can not use the same ...
11
votes
1answer
535 views

Bouncing Robots: Graphical Puzzle [closed]

Robots are indicated by the arrowhead shapes and the labels "r", "y", "b", "g". The label obviously corresponds to their color. The aim of the puzzle is to pick up the shapes and put them down in the ...
10
votes
11answers
12k views

Infinitely long loaf of Bread [closed]

You are visiting your old friend Mike at Infinitely's Baking Shop. Just as you arrived, he was taking out a fresh, infinitely long loaf of bread. Both of its ends extend infinitely long in a ...
10
votes
4answers
730 views

Prime Circuit Optimisation

It's logic gates time! You are only allowed to use NOT, OR, AND, XOR gates, accepting 1,2,2,2 inputs respectively. PART ONE You must build a circuit with $n$ inputs, and 1 output. The output must be ...
10
votes
3answers
1k views

Chess Game of Life

A bishop and a rook, of opposing colors, start on opposite corners on the same side of a chessboard, oriented as in the following picture: They then proceed to play a game of cat-and-mouse. Rules ...
10
votes
5answers
1k views

Knight on the keyboard

You are given a QWERTY keyboard, and are allowed to choose where you wish to start. You are only able type in the same way a knight is able to move on a chessboard (but in this case, on the keyboard). ...
10
votes
1answer
663 views

Dragons: Myth or MathJax?

Ever use MathJax to display mathematical expressions?   Expressions related to fractals? Ever used it to display fractals themselves?!   The time has come. These fractals are based on the ...
10
votes
1answer
455 views

Conway's Siege of Life

They are immortal and they are killing us. We may not be able to kill them, but we might be able to keep them occupied, distracted, for eternity. But we need to figure out how. Before there are no ...
9
votes
2answers
303 views

Create a 1 meter measure

How many folding steps do you need to create a $1 \, \text{m}$ measure from an ideal DIN A0 sheet? This sounds easy, but consider that this paper has edge lengths of $\sqrt[4]{2} \, \text{m}$ and $\...