Questions tagged [logical-deduction]

A puzzle that requires formal logical deduction to arrive at the solution. This suggests more than merely reasoning through clues to find an answer (you might want [situation] for that).

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What can I next logically deduce in Day 62 of the Minesweeper Advent Calendar? (Fake 3D)

So I have gotten back into playing the Minesweeper Advent Calendars on heptaveegesimal.com, and recently came across the 2023 Minesweeper Advent Calendar. I am currently trying to beat Day 62, which I ...
CrSb0001's user avatar
  • 1,590
24 votes
7 answers
3k views

The Devil's Shell Game

Inspired by the Skull Game in StoneStory RPG. You make a deal with the Devil. You are granted your deepest desire, in exchange, eventually, for your eternal soul. Every year, on your birthday, he ...
Hand-E-Food's user avatar
2 votes
2 answers
227 views

Lions vs. Pokémon

It is the year 10,000,000,000, and materalisation has been invented. At the same time, Nintendo has materialised every single Pokémon (countably infinitely many now!) to fight against finitely many ...
HelloWorld's user avatar
12 votes
1 answer
2k views

Add rules to Minesweeper until you can start with nothing

Think of classic Minesweeper game, with the following list of restrictions on the placement of mines: C (Connected): All mines are connected via 8-way neighborhood (orthogonal and diagonal). Q (Quad):...
Bubbler's user avatar
  • 12k
5 votes
1 answer
173 views

The Minesweeper Puzzle That Might Stump People

I thought this might be a different kind of puzzle. This is a game of Minesweeper that I played earlier today. All standard rules apply. For those who don't know, the number inside of each cell ...
Truej's user avatar
  • 512
1 vote
0 answers
223 views

5 guards, and get rid of the timer!

I like the lies and statistics question, but it is a bit too violent, so I suggest a (slightly harder) and way less violent version. You are looking at the basement of your house, and you see three ...
HelloWorld's user avatar
-2 votes
0 answers
93 views

Tasks and activities for gifted students in the 6th grades for a course on problem solving and the use of diverse strategies [closed]

I am a teacher at a gifted center up to middle school grades, and I am looking for interesting tasks and activities for gifted 6th grade students for a course on problem solving and using varied ...
Eran Alush's user avatar
7 votes
3 answers
1k views

Continue a hard Loopy/Slitherlink puzzle without brute-force

This is a classic Slitherlink puzzle from Simon Tatham's Portable Puzzle puzzle collection. I was stuck at the position shown for quite a while until I found a way to continue by logical deduction. I ...
quarague's user avatar
  • 1,841
5 votes
1 answer
407 views

A Spelling Bee Champion And Some Bewildered Children

At this year's International English Spelling Bee For 10 Year Olds, the contest came down to four children. The judges decided to give each child two words to spell. No two children were given the ...
Truej's user avatar
  • 512
8 votes
4 answers
748 views

Murder Mystery. Who is the killer?

There is a riddle about a Murder Mystery. My friend, who is studying law, gave me this puzzle. It was originally given to him by his professor, who often gives puzzles to his students. There are 7 ...
Curiospire's user avatar
-4 votes
1 answer
80 views

Make numbers 1 - 30 using the digits 2, 0, 2, 5

Try to make all numbers 1-30 using the digits 2, 0, 2, 5. Rules: Use all four digits exactly once. Allowed operations: $+,−,×,÷,! \text{ (factorial)}, !! \text{ (double factorial)}, !!! \text{ (...
WOWOW's user avatar
  • 165
7 votes
2 answers
455 views

A Colombian Jigsaw Sudoku

This is a Colombian Jigsaw Sudoku where the usual rules apply, but with irregular boxes. The dots in the right-hand scheme indicate how many of the numbers in a particular row or column are correctly ...
Xavier Castillo's user avatar
-1 votes
1 answer
260 views

Benny, Denny, Kenny and Lenny: Who lies and who tells the truth?

To allow new users to solve this puzzle and earn reputation points, I encourage all users whose reputation is 200 or more to not post an answer until 48 hours after this question is posted. Thank you! ...
Will Octagon Gibson's user avatar
13 votes
3 answers
726 views

Mr. Martin And The Mismanaged Airport Terminal

There is a small international airport in Greece. It has just 6 gates, lined up from 1 to 6 going away from the front desk. Tickets here only have the last names of passengers and gate numbers clearly ...
Truej's user avatar
  • 512
4 votes
1 answer
279 views

27 Directional Lights Celebrate 2024

Let us celebrate the start of 2024! (1 month late...) Direct each light (yellow) such that all unlit squares (white) are lit. Walls (black) block light from going through. Some clarifications of the ...
Sny Smartie's user avatar
  • 2,234
11 votes
1 answer
403 views

One more Colombian Sudoku

Here is one more Colombia Sudoku devised by Xavier Castillo. The usual sudoku rules apply. The dots outside the board above indicate how many cells in the corresponding column or row of that board ...
Bernardo Recamán Santos's user avatar
4 votes
1 answer
365 views

Creeper Lighting

There are two sets of similar but separate puzzles here; the white puzzle (with white cells) and the black puzzle (with black cells). Each puzzle is solved independently. Each number is a "...
Sny Smartie's user avatar
  • 2,234
9 votes
1 answer
588 views

Hardcore Lighting - Excalidraw

Each yellow cell is a light that shines in exactly one direction, horizontally, vertically, or diagonally, endlessly, and goes through any block as long as the block is not a wall. Black cells do not ...
Sny Smartie's user avatar
  • 2,234
16 votes
1 answer
723 views

Nurikabe: Back to basics

Rules of Nurikabe: Shade some cells in the grid. Each area of unshaded cells must contain exactly one number, which indicates the size of that area. Two unshaded areas may not share an edge, but they ...
Jafe's user avatar
  • 77.4k
7 votes
1 answer
348 views

Proving that a particular order is impossible

A friend shared this puzzle with me on Discord: There are 5 bowls, labelled 1, 2, 3, 4 and 5. The bowls can only be moved around in pairs without changing the order of the pair. The bowls can also be ...
user avatar
2 votes
1 answer
146 views

Unique day of the year

I made this challenge. Astronomers announced that the sky and the moon will appear violet-velvet next week, and one of their workmates is also celebrating her birthday on the day that the moon will ...
Thirdy Yabata's user avatar
-1 votes
1 answer
150 views

Minesweeper Queens

Based off of: Ken Duisenberg's Puzzle of the Week Oct. 15, 2003: Minesweeper Queens For the puzzle, in the given diagram, the numbered squares are empty, from which the given mines can be attacked by ...
CrSb0001's user avatar
  • 1,590
1 vote
1 answer
250 views

What‘s the next step to solve this 10x10 nonogram?

I got stuck on this nonogram (picross) from the game “Murder by Numbers”: What is the next step from here?
hb20007's user avatar
  • 845
3 votes
2 answers
193 views

Tatiana thinks of two numbers

My student Tatiana thinks of two positive integers, not necessarily different, none greater than 1000. I wish to determine her numbers, and for this she allows me any number of questions to which she ...
Bernardo Recamán Santos's user avatar
2 votes
0 answers
166 views

Guess Hat Collor [closed]

Five elders are sitting around a large bonfire. They know that Oluf will put a hat of one of four colours (red, green, blue or yellow) on each elder’s head, and after a short time for silent ...
Ali MohammadiNia's user avatar
15 votes
2 answers
2k views

Maximum number of pieces on a board

Suppose we have a 3x3 board. On this board, several squares are empty and several squares are filled with pieces. A legal move on the board is made using the same idea as taking in checkers: one piece ...
Ocelot's user avatar
  • 153
4 votes
2 answers
263 views

Beach Umbrellas puzzle: did I make a mistake or is Brainzilla wrong?

https://www.brainzilla.com/logic/logic-grid/beach-umbrellas/ has the following puzzle: Four families are going to the beach in the morning and are bringing their family-size umbrellas. Which family ...
Joseph Sible-Reinstate Monica's user avatar
2 votes
2 answers
721 views

On solving the minimally clued 8x8 Sudoku

So I have been doing research on the minimal amount of numbers needed to create an 8x8, and found this paper which went over the minimum amount of clues needed for a sudoku to have a unique solution ...
CrSb0001's user avatar
  • 1,590
26 votes
1 answer
1k views

Orange on Turquoise

This is part 50 of the puzzle series Around the World in Many Days. Each part is solvable on its own. Dear Puzzling, This is a Beaches puzzle (or tricolour Aquariums, if you prefer). Shade some cells ...
Jafe's user avatar
  • 77.4k
0 votes
1 answer
394 views

Special birthday

I made this challenge. Aica will celebrate her birthday next week. When she wrote the date format of her birthday in the form of M/D/YYYY, she noticed that her birthday will fall in a quarter of a ...
Thirdy Yabata's user avatar
11 votes
6 answers
9k views

Make numbers 1 - 30 using the digits 2, 0, 2, 4

Try to make all numbers 1-30 using the digits 2, 0, 2, 4. Rules: Use all four digits exactly once. Allowed operations: $+, -, \times, ÷, !$ (factorial), x^y (exponentiation), √ (square root). ...
jac's user avatar
  • 119
5 votes
1 answer
445 views

How to beat level 24 in Chessformer?

This is Level 24 in Chessformer: This is pretty easy to do at first, as long as you don't click the restart button (which I did by complete accident when I had some good progress on this level): ...
CrSb0001's user avatar
  • 1,590
2 votes
1 answer
378 views

Special wedding date and time

I made this challenge. Later this decade, Amelia and Jack operates a restaurant where they serve a lot of tasty meals and delicious product. Recently, their income from the restaurant is triple more ...
Thirdy Yabata's user avatar
14 votes
1 answer
266 views

! ! ! HNY 2024 ! !?

The following puzzle is a typical Sudoku 12 x 12 (1-9, a, b, c), but with an added twist. In addition to the standard rules, each colored box must also contain unique digits; no repetition is allowed ...
Xavier Castillo's user avatar
9 votes
2 answers
987 views

magic square operations

Fill in the grid with the numbers $1$ to $6$ so that each number appears exactly once in each row and column. A horizontal gray line marks any cell when it is the middle cell of the three consecutive ...
godlification's user avatar
3 votes
1 answer
88 views

Help with nearly finished expert sudoku

I just started with Sudoku and I jumped directly to a difficult level. I have a hint but don't want to use it. Please provide logic with your answer.
Steve's user avatar
  • 31
13 votes
1 answer
466 views

Happy and joyful 2024!

Fill each empty cell of the board on the left with a digit between 1 and 9. Each box and each column and row must contain all digits. The dots outside the board on the right indicate how many cells in ...
Xavier Castillo's user avatar
2 votes
1 answer
201 views

Variant on a Well-Known Card Puzzle

This is a variant on a well-known logic puzzle. It is not intended to be difficult, given that we are now officially in the “silly season”. Yesterday I won first prize in a Chess tournament, only to ...
happystar's user avatar
  • 7,534
0 votes
0 answers
73 views

Heuristic function for estimating nurikabe puzzle state

I am trying to write a program for solving nurikabe puzzle. I need a method to approximately represent the state of the game in one number, to choose the best way for the algorithm to continue. I can'...
Papouc's user avatar
  • 1
-2 votes
1 answer
96 views

Find the odd one out (at maximum one item) [closed]

This is a set (not series or sequence): x,y,z,x,z Which doesn't fit? We need the most basic and logical answer why the chosen item in the specified set doesn't fit in.
Archipelago's user avatar
5 votes
1 answer
233 views

Decent Knights - Chess

In Naughty knights it’s asked to prove that it’s impossible to fit more than 32 knights such that no knight attacking other. Can you find the minimum number of knights, filling the table in a way that ...
ulutku's user avatar
  • 151
12 votes
1 answer
345 views

The Island of Careful Thought

Everyone who lives on the Island of Careful Thought is either sane (believing all true statements, and no false statements) or insane (believing all false statements, and no true statements). The ...
Misha Lavrov's user avatar
  • 1,911
10 votes
6 answers
845 views

Organising a tournament

In a table tennis tournament, there are 7 different tables and 10 players. Every player has to play exactly 7 matches (one match at each table). It's not allowed to play twice against the same ...
Simd's user avatar
  • 7,816
4 votes
2 answers
202 views

Looking for the name of a specific numerical logic puzzle. Involves swapping digits for shapes

I took an online assessment for a job and there was this really interesting section where you had to solve simple algebra problems, except the digits (not the numbers) were replaced by symbols. An ...
TheJeran's user avatar
  • 141
17 votes
1 answer
620 views

Wreck Exploration

This is part 48 of the puzzle series Around the World in Many Days. Each part is solvable on its own. Dear Puzzling, The larger grid here is a Takuzu puzzle (also known as Binairo). Fill the grid ...
Jafe's user avatar
  • 77.4k
4 votes
1 answer
195 views

How to beat Level 25 in Flip Palace?

Flip Palace is a minimalist game developed by 08jack where you flip into the walls and solve puzzles. The goal of Flip Palace (stolen from the description): flip into the walls, solve puzzles This ...
CrSb0001's user avatar
  • 1,590
18 votes
3 answers
3k views

Naughty knights

Recently the British newspaper The Guardian published the following puzzle, titled Naughty Knights: And here's the solution published by the newspaper later: Unfortunately, this solution doesn't ...
Mitsuko's user avatar
  • 2,025
14 votes
2 answers
857 views

PSE Advent Calendar 2023 (Day 20): Candles on the tree

This puzzle is part of the Puzzling Stack Exchange Advent Calendar 2023. The accepted answer to this question will be awarded a bounty worth 50 reputation.< Previous Door Next Door > Rules of ...
Jafe's user avatar
  • 77.4k
1 vote
1 answer
94 views

How do I do the Hard mode version of the 2nd bonus puzzle unlocked after beating level 45 in Hexologic?

In Hexologic, there are bonus levels that you can unlock after completing each 15 levels. (although it doesn't matter if it's on Easy or Hard mode) I have been able to complete all of the bonus levels ...
CrSb0001's user avatar
  • 1,590
6 votes
1 answer
519 views

PSE Advent Calendar 2023 (Day 18): A holly jolly Hexologic

This puzzle is part of the Puzzling Stack Exchange Advent Calendar 2023. The accepted answer to this question will be awarded a bounty worth 50 reputation.< Previous Door Next Door > Rules: ...
CrSb0001's user avatar
  • 1,590

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