Questions tagged [no-computers]

A puzzle designed to be solved without using calculators, online decoders, or computer programming. Using a computer to type and post the answer is allowed; the spirit of this tag is to make people solve the puzzle on their own.

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12
votes
3answers
1k views

Swapping 3 knights in a 4x4 grid

Can you swap black and white knights in this 4x4 grid? There is one important constraint: at no point can a knight be under attack by an opponent knight. Knights move using standard chess moves (L ...
12
votes
2answers
433 views

Wormeus and the Pink Lady Stickotaur

Wormeus lives in a labyrinth containing lots of apples. His main ambition in life is to eat as many apples as possible but his nemesis, the evil Pink Lady Stickotaur, has other ideas – if you pardon ...
19
votes
1answer
631 views

Quartum non datur

Can you give a good rational approximation of $$\sqrt[3]2 \times \sqrt[4]2$$ without doing any significant maths? Hint: Attribution: Mine.
9
votes
2answers
818 views

Don't bully your little sister at chess

This puzzle was inspired by @RewanDemontay's puzzle De-zephyr The Solution!. Rewan kindly granted me permission for making this puzzle and citing his as my source of inspiration. I thought of naming ...
2
votes
0answers
198 views

This ᴀɴᴅ That musical act from the past [closed]

Below is a fill-in-the-blanks three-part list of variously-venerable musical acts of the form “________ ᴀɴᴅ ʜɪs/ᴏᴜʀ/ᴛʜᴇ _________.” The example of “Paul Revere ᴀɴᴅ ᴛʜᴇ Raiders” has been filled in for ...
14
votes
1answer
575 views

Candy Button Paper

An entry in Fortnightly Topic Challenge #35: Restricted Title 1. Title based on this xkcd. Your biggest dream has come true: you have an infinite supply of your favorite five-flavor candy button ...
12
votes
1answer
432 views

AnaCross: A crossword made of anagrams

This is a new type of puzzle I've devised: the AnaCross. Nothing new under the sun and all, I'm sure someone has made one before, but I've never seen it. The rules are pretty simple. At the end of ...
1
vote
1answer
230 views

Probability of a successful DT Cannon

In multiplayer Tetris, there are a number of opening setups that let you send powerful attacks very quickly. One popular opening is the DT Cannon, which allows the player to very quickly send a T-Spin ...
12
votes
1answer
214 views

Three white queens, two white knights, and one rook on a chess board

On an 8 x 8 chessboard, place three white queens, two white knights, and one white rook so that every cell of the board is under attack by at least one piece not standing on it. Source: https://www....
3
votes
1answer
159 views

Non-increasing arrangement

We are arranging the numbers from 1 to 8 in an order so that three consecutive terms cannot be increasing. For example, 12345678 isn’t allowed but 81436572 is. How many ways are there to do it? Please ...
20
votes
1answer
478 views

Escape from Sudoku!

An entry in Fortnightly Topic Challenge #50: Escape Rooms I hesitated to enter this in the Escape Room FTC, but I definitely was inspired by the challenge to create this puzzle, and it is, in some ...
4
votes
1answer
1k views

Find three ways of forming the number 100 using 3,3,5,7

As it says in the title. Rules: anything not explicitly allowed is forbidden. use 3, 3, 5, 7 and multiplication, division, sum, difference, unary minus, and exponentiation in any order. Parentheses ...
4
votes
1answer
162 views

Chess - I will eat!

Suppose that you are playing White, and your aim is to eat a black piece (pawns qualitfy) in the fewest moves as possible and Black are not cooperating at all, and, even more, Black's aim is to ...
13
votes
1answer
2k views

A Math Riddle: But the math does not add up

Grandpa had a lot of different books of stamps on his desk. He was counting them. I was curious. “What are all those stamps Grandpa?” “I just got back from the Post Office son and bought a bunch of ...
9
votes
1answer
403 views

Trivia... sudoku

An entry in Fortnightly Topic Challenge #49: Pub Quiz Camouflage Please do not search the answers online (hence the no-computers tag), otherwise it would be too simple to solve this puzzle. I tried ...
5
votes
4answers
6k views

Special 5x5 Sudoku-like table

This is a special 5x5 Sudoku-like table. Each row, column, and diagonal contains digits from 1 to 5 (including diagonals obtained by wrapping around the edges). To filter duplicates (by rotation, ...
30
votes
5answers
5k views

How can 3 queens control the white squares?

It is well known that there is no way of arranging 4 queens on a checker board in such a way that every square is occupied or threatened. Now consider a slight variation where we only need to cover ...
6
votes
2answers
339 views

Twin primes and divisibility

Let $p$ and $q$ be a pair of twin primes. Find the smallest possible value of $a+b$ where $a$ and $b$ are positive integers such that $p\;|\;(a+qb)$ and $q\;|\;(a+pb)$. This puzzle is my own ...
3
votes
2answers
510 views

A greedy cryptarithm

Find all solutions to EAT ATE + EATEN ------- YUMMY Where different letters represent different digits from 0 to 9. Problem by myself
2
votes
1answer
86 views

Number conversion via Prime route

This is a variation of the Word Ladder. Instead this is a number ladder. Convert the number 12345 to the number 54321 in seven or less steps with the following rules A: You can only change any one ...
17
votes
4answers
2k views

Paint 21 Squares of a 7×7 Board Without Forming a Rectangle

Got a nice puzzle from my friend, when he was competing in IWYMIC/IMC 2011. Paint $21$ of the $49$ squares of a $7 \times 7$ board so that no four painted squares form the four corners of a rectangle....
4
votes
0answers
353 views

Around The World

It's White to move and win against Black. Black plays optimally. Have fun! Oleg Pervakov and Karen Sumbatian, Shakmaty v SSSR 1990 P.S.-To me, it’s crazy that the title hasn’t been taken yet! Hint:
9
votes
1answer
272 views

Chess Endgame Study

I came across this puzzle-like endgame study. Usually, opposite color bishops are draw-ish. Here's an absolutely extraordinary counter-example. Enjoy! White to play and mate in 8. Source: Winning ...
0
votes
0answers
49 views

An orderly transition of power [duplicate]

Since it's the 20th of January, perhaps we can demonstrate an orderly transition from TRUMP to BIDEN? There are eight steps to get there and all words are found in the World Scrabble dictionary. One ...
7
votes
1answer
211 views

Three to Seven in five or less

Can you change the word Three to the word Seven in five steps or less with the following rules: You must exactly replace two letters; one vowel and one consonant of the word in each step with a ...
8
votes
3answers
393 views

With a little effort, one can prevail

What is common between the following words and names? (Inspired by this except that I actually know the answer to this one) Defeat Kleenex? Guanaco Nerdiest Sardar Ian McKellen Dingo Gun Diablo ...
7
votes
1answer
237 views

Expanding on a classic

From the simple caesar to the seemingly uncrackable elliptic curve, there are countless ways to obscure - and even hide - a sensitive message. Cryptography is quite interesting in this way. I find the ...
0
votes
0answers
93 views

First digit of 2021^2021 [duplicate]

Can you find the first digit of $2021^{2021}$ without a computer? Good luck!
7
votes
1answer
502 views

A special number

Here is a nice puzzle from my friend. Can you find a number that is a product of two consecutive primes and when multiplied by its own reversal produces a palindrome? The answer may surprise you. No ...
5
votes
3answers
351 views

A Circle of numbers

Just saw a Circle of numbers on my Whats App message (source not listed) which is as following Arrange numbers 1 to 32 in a circle such that any two adjacent (neighboring) numbers add up to a perfect ...
8
votes
2answers
380 views

Rack 'Em Up! 🎱

In a game of English eight-ball pool, a set of 15 balls are arranged or 'racked' in the shape of an equilateral triangle. In order for the balls to be racked fairly, they must be arranged like so: <...
35
votes
3answers
7k views

First digit of 3^2020

Inspired by The last digit for 3^(2019) Can you find the first digit of 32020 without a computer?
4
votes
1answer
149 views

Find the fastest stalemate for Black!

In the below position, how many moves will it take for Black to be stalemated? Black moves first, and both sides are working together. Black's pawns are moving down. Have fun solving! Zdravko Maslar, ...
6
votes
1answer
207 views

Down The Board-Selfmate In 10 Moves

Here's a miniature selfmate puzzle that I composed today. I just got an idea and I managed to successfully create it. I got the basic idea down to just 9 pieces, none of which are promoted. It's White ...
6
votes
1answer
272 views

An Artistic Bunch

Luke, Clive, Anton and Paul are four talented creative artists, one a dancer, one a painter, one a singer, and one a writer. (Though not necessarily respectively.) Luke and Anton were in the audience ...
7
votes
2answers
1k views

I have a bad feeling about this country name

What is the longest country name that can be fully anagramed into one word from the Merriam-Webster dictionary? Please use this site for the list of countries. Minimum length 8 letters. If a country ...
17
votes
9answers
5k views

Solitaire Chess

A friend of mine got me Solitaire Chess for Christmas years ago. I set up the board below. Is it possible to solve it? If so, what is the solution? (No programs allowed- Use only your brain.) Rules: ...
7
votes
2answers
349 views

Pentomino tiling on wrap-around 5x5 grids

It is known that P pentominoes cannot tile a 5x5 square board. Q1: If the east and west edges of the 5x5 square board are "wrapping around" (if you move a piece through one of the edges, the ...
2
votes
4answers
473 views

Crossing out every second number

Write down all integers from 1 to 1000. Cross out the first number and every second number after that. So you will cross out 1, 3, 5 and so on. Now repeat the process exactly - cross out the first ...
3
votes
1answer
216 views

n rows and 18 columns

I haven't posted for a long long time, so here is an interesting combinatorics problem! There is a table with 𝑛 rows and 18 columns. Each of its cells contains a 0 or a 1. The table satisfies the ...
7
votes
1answer
254 views

Stochastic Taxicab Path

A city's roadworks is laid out as a perfectly rectangular tiling. A commuter within this city has to travel to work a distance of 17 blocks east and 7 blocks north each day, and tries to take the same ...
12
votes
2answers
416 views

A fraction puzzle

This is a puzzle with both the computer-puzzle tag and the no-computers tag. We have the following list of five fractions: $$11/5, 30/77, 1/11, 21/2, 5/7.$$ Starting with an integer $x$, we perform ...
2
votes
1answer
117 views

Does this alphametic have only one solution?

I could only get one answer for the following alphametic. Can you confirm? ETAS / (E * T * A * S) = SEAT - SATE All 4 lettes are separate digits from 1 to 9. ETAS, SEAT and SATE are 4 digit numbers ...
3
votes
2answers
246 views

Yet another mixed sum

An instance of this puzzle is here: https://www.theguardian.com/science/2020/nov/16/can-you-solve-it-the-srcmalbed-nmebur-plzuze a) It has been swhon taht to raed a txet the oedrr in wihch the ...
13
votes
1answer
556 views

The tip of a colorful triangle

Original source: Problem 1 of British Informatics Olympiad 2017, Round 1 You're given a bunch of red (R), green (G), and blue (B) balls. I arrange some balls on a line. Then I ask you to complete the ...
13
votes
3answers
2k views

Want to go from MANILA to UGANDA

How do you get from the word MANILA to UGANDA in the shortest time? You can change up to 3 letters at a time to form a new 6 letter word which MUST be either a country name or a capital of a country. ...
10
votes
10answers
4k views

A Body Part inside another Body Part

In one of his silly question moods, Grandpa says: "Can you name a body part that is entirely inside (within) another body part but some distance away?" Taking the clue from his last question ...
7
votes
7answers
311 views

Chess Construction Challenge #3-The Inverse Babson

Another day, another task! Today's challenge is to construct four positions, with White to move and win, such that: In each position, White's move is to promote to a particular piece, for a position ...
19
votes
1answer
857 views

Honeybee Hangover

A drunken honeybee lands on a completely random hexagon of a large triangular section (depicted below) of its hive, and then every second afterwards, takes a step to a completely random adjacent ...
5
votes
1answer
178 views

Particular Diophantine equation [closed]

There are four natural numbers $a$, $b$, $c$ and $d$ such that $a<b<c<d$. They satisfy the following equation: $a^2$+$b^2$+$c^2$+$d^2$= $abcd$ What is the smallest possible value of $d$? This ...

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