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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6
votes
1answer
270 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 ...
7
votes
1answer
235 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 ...
7
votes
2answers
342 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
462 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
215 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
251 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 ...
2
votes
1answer
112 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 ...
12
votes
2answers
412 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 ...
3
votes
2answers
245 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
553 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 ...
18
votes
1answer
841 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
177 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 ...
5
votes
2answers
187 views

7x7 Knight's tour: Minimal proof for universality on black squares

We already know that 7x7 board cannot have a closed Knight's tour, and it cannot start or end at a white square if R1C1 is black. But our knowledge about 7x7 Knight's tour is still limited. So here is ...
0
votes
1answer
120 views

The largest lettered word which you can make and continue make words from it by deleting $1$ letter from it everytime [duplicate]

Ok, here is a simple puzzle to think :- Find the largest lettered word such that deleting one letter at a time can give you a meaningful word in each step . Note that only deletions are allowed, in ...
12
votes
2answers
447 views

The art of computer programming

EDIT: I know we are not supposed to edit in new requirements after first posting but as far as I understand it this requirement is implicit in all questions here: Explain your answer! At least a ...
6
votes
1answer
114 views

Sudokus everywhere 2

Every 9x9 box is a valid sudoku, making 4 sudokus in all. Hopefully this one is a little more challenging than the previous one. I tried keeping the clues symmetric, but didn't quite manage. Enjoy!
43
votes
5answers
9k views

TRUMP to BIDEN : This transition won't be easy

Can you change the word TRUMP to the name BIDEN in 10 steps or less by changing one letter at a time? Each change must result in a valid word from MW dictionary. No proper nouns, abbreviations or ...
18
votes
1answer
787 views

Sudokus everywhere!

Every 9x9 box is a valid sudoku, making 9 sudokus in all. I'm not sure how hard it is as I started solving it with just a few clues, then added more whenever I got stuck. Enjoy!
9
votes
2answers
187 views

4x4 grid equations version 2

I decided to make another one of these, because they are fun and this one is rather different. Can you place all numbers from 1 to 16 into cells, such that the following 8 equations hold? Note that ...
10
votes
1answer
599 views

4x4 grid equations

Can you place all numbers from 1 to 16 into cells, such that the following 8 equations hold? Note that the operator "/" only works for non-remainder division, i.e. you can have "8 / 4&...
12
votes
1answer
505 views

An odd looking Sudoku

Somewhat in the spirit of Stiv's This new puzzle type needs a name, can you solve this odd looking Sudoku and give it a name?
4
votes
0answers
186 views

What is the shortest English–language sentence which contains 25 unique letters? [closed]

There is a lot of literature on the subject of short English pangrams, that is, sentences that contain every letter. But I am curious what the shortest, or at least some of the shortest, sentences are ...
13
votes
4answers
2k views

77-digit number divisible by 7 with seven 7s

The smallest number divisible by 7 with seven 7s is trivially 7777777. Then, what is the greatest 77-digit number divisible by 7 which contains seven 7s?
6
votes
3answers
564 views

How to divide their loot? The thieves' dilemma

Three thieves rob a jewelry store at gunpoint and end up with the following loot. 10 necklaces 8 bangles 6 rings It so happened that the jewelry was antique and valuable. They asked the scared ...
3
votes
1answer
227 views

Will forcing chains break this sudoku puzzle?

I am trying to pick up advanced sudoku techniques by practicing with “difficult” puzzles as suggested by my sudoku app. In this puzzle, I am stuck in the position as shown below. I think I can make ...
0
votes
2answers
238 views

Coffee theorem puzzle [duplicate]

I am back yet with another puzzle, my last one was made this morning, and this one is a copied one from an app/website called Brilliant. So, this is especially for those who do not have Brilliant ...
7
votes
4answers
1k views

Change Four to Nine in fewest steps

Change the word FOUR to the word NINE by changing only one letter at a time. The change must result in a 4 letter word from the MW dictionary and cannot be an abbreviation,acronym, anagram or a ...
20
votes
2answers
1k views

Sudoku in the third dimension (3D Sudoku)

People seemed to enjoy my last Sudoku variant puzzle - Samurai Pseudoku, so I spent this week making another! This one is going to require using logic you've never used before... The last one was a ...
9
votes
1answer
298 views

Multiplying to reverse digits

Today I noticed that $294$ is a multiple of $49$, which is the last two digits of $294$ reversed. How many other numbers have this property? That is, how many three-digit numbers have a factor which ...
3
votes
2answers
507 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
7
votes
1answer
234 views

Balancing a yardstick

There is a known trick to this, so “no computers” may be used to look up the answer. Alice gives Bob a wooden yardstick with a small weight secured to one end and says, “See if you can find the ...
60
votes
2answers
4k views

Sudoku like you've never seen it before

I've spent this week trying to create a difficult logic puzzle which is a combination of two Sudoku varaints, 'Samuari Sudokus' and 'Pseudokus', and this combo is unlike anything you can find online. ...
7
votes
2answers
368 views

Unlock the safe!

There is a (very insecure) safe, which has three digits in the lock. Each digit can only be $0,1,2$. The user choose a password made up with three $0,1,2$ digits, and the safe can be unlocked if at ...
9
votes
1answer
390 views

The Lucky Number

Lucky numbers are 4 digit numbers that have the following property: they are equal to the sum of the fourth power of their digits. Therefore, they can be expressed as follows: $$1000a+100b+10c+d = a^4+...
11
votes
1answer
283 views

Regarding the universe; life, death, neutrons, stars; everything

My brother Yzarc recently returned from his summer road trip, so I went to visit him. He seemed unusually quiet, sitting pensive in a chair and watching the clouds. This was unusual, since typically ...
4
votes
2answers
159 views

Computer Puzzle - Arithmetic Of The Day

Harou, a Japanese teacher in the school, noticed a ship made of paper outside her office. When she unfolds the paper, she saw something strange. There is something that looks like a riddle, followed ...
3
votes
2answers
139 views

Cube the digits and carry on

Take a number between 2001 and 2100 inclusive. Cube the digits of the number and add them together, then repeat the process with the new sum and restart the process over and over. For example if I ...
1
vote
2answers
144 views

Solve the magic square

My friend gave me the following magic square to solve $$\begin{bmatrix}\frac23&5&?\\\frac19&?&?\\?&?&?\end{bmatrix}$$ I can solve it. Can you? You must provide logical ...
8
votes
1answer
393 views

Whose birthday is it?

A group of people have gathered for a birthday celebration. Their ages are related as follows: The product of the 1st person's and the 2nd person's ages is $311\frac{2}{3}$ plus the 3rd person's age. ...
6
votes
2answers
194 views

I'll give you the instructions, you give me the answer

- perform handshake - install es on both ends - pause process in exce - swap chang.exe - combine previous and modify - terminate communication Hint 1
6
votes
3answers
346 views

A Kind of Unique Prime Number

A Prime number with the following properties Less than 7 digits and more than 3 digits ALL digits in the number are Prime numbers-- some repeated. All individual digits in the number add up to a ...
17
votes
2answers
374 views

What to make of $\!\:\tt puzzle.\!txt$?

Puzzling Stack Exchange: Don’t even ask where I found the old printout, below, of an uncommented computer program. As I am a leading-edge software solutionaut hone-tuned for elegantly annotated ...
15
votes
1answer
312 views

Words with Alchemists

You are probably familiar with Word Ladders, where you attempt to transform one word into another by switching one letter at a time, with each transformation forming a new word. This puzzle is similar....
7
votes
2answers
591 views

Letters to Numbers: What goes in the blank circle?

This is a letter to number conversion and pattern puzzle. What number goes in the blank circle and why? Each letter is a distinctly seperate digit from 0 to 9. ( There are 10 letters representating ...
6
votes
0answers
114 views

Hand tiling - 4x inflated pentominoes with pentominoes and tetrominos

This is a manual tiling puzzle. Difficulty level always hard to estimate, but I would say a few minutes per solution for an accomplished solver, all the way to just about impossible for someone like ...
35
votes
6answers
5k views

too easy puzzle? Try it first!

Arrange the numbers $1$ to $9$ to replace letters $A$ to $I$ so: $(A+B+C+D)-(E+F+G+H) = I$ Too easy? Too many answers? Try it first! Then explain why.
4
votes
2answers
220 views

Can you find the key move?

I've created this chess problem for today. it's White to move and their pawns move upward. Can you find the key move? Have fun, and no computers are allowed! Checkmate In 5 Moves
7
votes
3answers
218 views

Perfect power nim

Let $m,n$ be positive integers. Ann and Ben has $m$ stones, and each of them takes exactly the perfect power of $n$ stones ($n^k$, where $k$ is a nonnegative integer) in order, starting from Ann. Who ...
8
votes
4answers
496 views

The broken wheel

In a regular polygon, we can connect six of the vertices to form a convex hexagon. I construct a hexagon by picking six vertices out of a regular $n$-sided polygon. In this hexagon, if you connect the ...

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