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.
623
questions
0
votes
1answer
102 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
387 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
96 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!
41
votes
5answers
8k 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
756 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
167 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
529 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
460 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
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 ...
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
516 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
200 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
156 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 ...
17
votes
2answers
978 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
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 ...
2
votes
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
votes
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 ...
57
votes
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. ...
7
votes
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 ...
9
votes
1answer
366 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:
$$1000a+100b+10c+d = a^4+...
11
votes
1answer
247 views
Regarding the universe; life, death, neutrons, stars; everything
My brother Yzarc recently returned from his summer road trip, so I went to visit him.
He seemed unusually quiet, sitting pensive in a chair and watching the clouds. This was unusual, since typically ...
4
votes
2answers
149 views
Computer Puzzle - Arithmetic Of The Day
Harou, a Japanese teacher in the school, noticed a ship made of paper outside her office.
When she unfolds the paper, she saw something strange.
There is something that looks like a riddle, followed ...
3
votes
2answers
135 views
Cube the digits and carry on
Take a number between 2001 and 2100 inclusive. Cube the digits of the number and add them together, then repeat the process with the new sum and restart the process over and over. For example if I ...
1
vote
2answers
134 views
Solve the magic square
My friend gave me the following magic square to solve
$$\begin{bmatrix}\frac23&5&?\\\frac19&?&?\\?&?&?\end{bmatrix}$$
I can solve it. Can you?
You must provide logical ...
8
votes
1answer
373 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
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
6
votes
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 ...
16
votes
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 ...
15
votes
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
votes
2answers
553 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
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 ...
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
204 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
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 ...
8
votes
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 ...
3
votes
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
votes
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 ...
4
votes
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, ...
3
votes
2answers
265 views
7
votes
3answers
414 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 ...
10
votes
2answers
1k views
Escape from your friend!
I saw this interesting problem in a Mathematics book in Chinese(I translated it):
You and your friend is playing a game. There is a square swimming pool, and you are in the middle of it. Your friend ...
9
votes
1answer
362 views
Mini 8 queens puzzle
On a 5x5 chessboard, place 5 black queens and 3 whites queens so that no queens are attacking those who are of different color. Furthermore, the numbers indicate how many queens are attacking the ...
5
votes
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 ...
9
votes
2answers
250 views
Square made up with polyominoes
A 3 x 6 rectangle has 2 holes in it as shown. Can you cut it into 3 polyominoes with different areas so that they can form a square? The pieces can’t be flipped when they form the square and two ...
13
votes
3answers
767 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 ...
4
votes
1answer
168 views
Can you fill $3 \times 3$ magic square?
In the magic square
Each number in the matrix is unique and natural.
Each row, column and the two diagonals add up to the same number (the magic constant).
Can you fill in the missing numbers?
\...
14
votes
1answer
622 views
The numbers on blackboard
The numbers $2020,2019,2018,...,1$ are written on the blackboard from left to right.
John repeats the following process until there is only one number left:
John chooses the first two numbers from ...
3
votes
1answer
103 views
Find the unique passcode
"Is this the Coldport Lost Property Office? I think I left my puzzle-book on the train this morning, and I was hoping someone had handed it in." The speaker was a tall gentleman with a six-...
3
votes
2answers
437 views
A Puzzle about “Codeforces Subsequences”
I'm quite intrigued by an "easy" problem in recent Codeforces contest: Codeforces Subsequences.
In this problem, you have to create a string $T$ as shortest as possible such that $S = $ &...
