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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3
votes
1answer
143 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 ...
9
votes
1answer
131 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....
4
votes
1answer
130 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
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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 ...
8
votes
1answer
347 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, ...
31
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
333 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 ...
10
votes
1answer
325 views

A Cryptic Cryptarithm

An entry in Fortnightly Topic Challenge #48: Unusual tag mix Solve these puzzles to reveal why I made them. Matriarch mostly prepared oats for American airline location? (8) AIRLINE + LOCATION = ? 51 ...
3
votes
2answers
503 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
75 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
347 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
255 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
44 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
184 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
372 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
225 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
89 views

First digit of 2021^2021 [duplicate]

Can you find the first digit of $2021^{2021}$ without a computer? Good luck!
7
votes
1answer
496 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
271 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
353 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
6k 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
139 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
201 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
262 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
4k 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
336 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
441 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
204 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 ...
6
votes
1answer
238 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
389 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
107 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
242 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
536 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
298 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 ...
17
votes
1answer
825 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
174 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
167 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 ...
3
votes
1answer
355 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
votes
2answers
433 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
votes
1answer
115 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 ...
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 ...
6
votes
4answers
498 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
votes
1answer
109 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!
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. ...
18
votes
1answer
780 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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