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.
645
questions
0
votes
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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
175 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 ...
0
votes
0answers
88 views
First digit of 2021^2021 [duplicate]
Can you find the first digit of $2021^{2021}$ without a computer? Good luck!
9
votes
3answers
358 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
...
5
votes
3answers
266 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 ...
7
votes
1answer
494 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 ...
8
votes
2answers
347 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:
<...
5
votes
1answer
133 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
257 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
217 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
335 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
433 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
201 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 š rows and 18 columns. Each of its cells contains a 0 or a 1. The table
satisfies the ...
6
votes
1answer
237 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
103 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
...
11
votes
2answers
383 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
241 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 ...
asked Nov 17 '20 at 19:17
Bernardo Recamán Santos
11.8k2 gold badges21 silver badges110 bronze badges
13
votes
1answer
534 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 ...
17
votes
1answer
815 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
172 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
160 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
114 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
427 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
108 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
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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
779 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
171 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
553 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
487 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
180 views
What is the shortest Englishālanguage 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
541 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
216 views
Will forcing chains break this sudoku puzzle?
I am trying to pick up advanced sudoku techniques by practicing with ādifficultā 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
187 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
281 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
444 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
226 views
Balancing a yardstick
There is a known trick to this, so āno computersā may be used to look up the answer.
Alice gives Bob a wooden yardstick with a small weight secured to one end and says, āSee if you can find the ...
60
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
358 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
373 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:
$$1000a+100b+10c+d = a^4+...
11
votes
1answer
260 views
Regarding the universe; life, death, neutrons, stars; everything
My brother Yzarc recently returned from his summer road trip, so I went to visit him.
He seemed unusually quiet, sitting pensive in a chair and watching the clouds. This was unusual, since typically ...
4
votes
2answers
153 views
Computer Puzzle - Arithmetic Of The Day
Harou, a Japanese teacher in the school, noticed a ship made of paper outside her office.
When she unfolds the paper, she saw something strange.
There is something that looks like a riddle, followed ...
3
votes
2answers
138 views
Cube the digits and carry on
Take a number between 2001 and 2100 inclusive. Cube the digits of the number and add them together, then repeat the process with the new sum and restart the process over and over. For example if I ...
1
vote
2answers
140 views
Solve the magic square
My friend gave me the following magic square to solve
$$\begin{bmatrix}\frac23&5&?\\\frac19&?&?\\?&?&?\end{bmatrix}$$
I can solve it. Can you?
You must provide logical ...
8
votes
1answer
384 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
192 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
343 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 ...
