Questions tagged [no-computers]

A puzzle designed to be solved without using calculators, online decoders or computer programming. You're still allowed to use a computer to post the solution; Stack Exchange doesn't support smoke signals yet.

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3
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1answer
128 views

Particular Diophantine equation

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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2answers
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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 ...
3
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1answer
345 views

Solve the Lyne puzzle

This puzzle comes from the game Lyne. The rules: Start and end at the shape with a white dot in the middle Only connect same colours together Lines cannot cross each other All points must be ...
12
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2answers
401 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 ...
0
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1answer
105 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 ...
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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 ...
6
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4answers
493 views

Backwards pawns

Part One: Reach the above position from the starting position Part Two: Find the fastest way to get to this position. Answering part one will get you an upvote, answering part two gets the checkmark!
6
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1answer
99 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!
57
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2answers
3k 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. ...
18
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1answer
762 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!
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2answers
168 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 ...
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2answers
836 views

Move 2 or 3 spaces in this 5 by 5 grid

You have a 5 by 5 Board as shown. You start from the S (Center) position. You can: 1 Move TWO or THREE spaces only 2 You can move Vertically or Horizontally or Diagonally but only in a straight ...
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1answer
533 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
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1answer
466 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?
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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?
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0answers
171 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 ...
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3answers
518 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 ...
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1answer
201 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
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2answers
158 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 ...
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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 ...
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2answers
985 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 ...
7
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1answer
221 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 ...
9
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1answer
270 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 ...
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2answers
437 views

A greedy cryptarithm

Find all solutions to $$\begin{array}& & & &E&A&T\\& & &A&T&E\\+&E&A&T&E&N\\\hline&Y&U&M&M&Y\end{array}$$ Where ...
7
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2answers
349 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 ...
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1answer
247 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 ...
9
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1answer
367 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+...
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2answers
149 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 ...
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1answer
374 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. ...
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2answers
135 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 ...
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2answers
134 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 ...
13
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3answers
768 views

Pythagorean triplets wheat field

A rectangular field has width $a$ and length $a+1$. We cut it into 3 triangles that all have integer side lengths. If all triangles have a different area, then what’s the minimum value of $a$? Please ...
6
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2answers
188 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
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3answers
338 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 ...
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2answers
206 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
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2answers
340 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 ...
35
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12answers
9k views

Ten girls around a table

Ten girls are sitting around a table. Each of them picks a real number and whispers it to the two neighbors immediately to the left and to the right. (Hence: each girl communicates one number, and ...
15
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1answer
292 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
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3answers
416 views

The Eighth Color

For this puzzle I've made, guess what is the missing color. You can't use a computer to find the solution. But once you know you have it, you are allowed to use a computer, mostly to select a RGB ...
8
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4answers
481 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 ...
35
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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.
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2answers
554 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
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0answers
93 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 ...
7
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3answers
212 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 ...
3
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1answer
130 views

Fill in numbers on the cube … again!

You are given a cube. You are told to fill in each face randomly with some of the numbers $4, 5, 6, ..., 11$, with no repetition. What is the probability that for each two faces that are connected by ...
19
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1answer
3k views

Today is a sad day

Today is a sad day - Today, it was supposed to be my big day to shine! But unfortunately that is no longer the case. I have heard from others here that puzzle-making is a great way to drown out one's ...
6
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2answers
329 views

Tempoverlustspiel

Tempoverlustspiel-A German word that roughly translates to "loss of tempo game." An interesting chess term that I leaned a while ago. With White to move in the below position, how many moves ...
4
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1answer
162 views

Fill in numbers on the cube!

You are given a cube. You are told to fill in each vertex with the numbers $4,5,6,...,11$, with no repetition. What is the probability that for each two vertices that are connected by a common edge, ...
5
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3answers
861 views

4k reputation special: “I hate square numbers!”

There is a large prison, with exactly 4000 prisoners. The warden noticed that there were too many prisoners, so they lined up all the prisoners, and repeated the following procedure until less than ...
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2answers
265 views

Elementary word-search

Here's a simple wordsearch: ...and the text version: ...

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