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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7
votes
1answer
52 views

The Nurikabe of Peace

Today is the 75th anniversary of Sir Winston Churchill's speech "The Sinews of Peace" which introduced to the world the phrase "The Iron Curtain". This puzzle is inspired by that ...
7
votes
4answers
673 views

Sorting 6 boxes by selecting 3 boxes each time

There are 6 boxes, each containing a distinct number. You can select 3 boxes and the Oracle will tell you which box has the smallest number and which has the largest number of the three selected boxes....
8
votes
2answers
176 views

Double sudoku - two-digit numbers, the 1s and 10s places both form Sudokus [closed]

Using distinct 2-digit numbers from 11-99 that have no zeros, fill in the grid so that the tens digits form a Sudoku and the units digits form a (different) Sudoku. There might be a mathematical way ...
1
vote
5answers
155 views

Another (simple) self-referential aptitude test

Nine months ago I started my journey on Puzzling in a rough way with this question. I honesty hope this time I won't generate so extended discussion...! I love self-referential questions, puzzles or ...
19
votes
1answer
305 views

Escape from Sudoku!

An entry in Fortnightly Topic Challenge #50: Escape Rooms I hesitated to enter this in the Escape Room FTC, but I definitely was inspired by the challenge to create this puzzle, and it is, in some ...
-1
votes
0answers
88 views

Hard IQ Test Puzzle [closed]

Can someone please help me to find the answer to the puzzle?
-3
votes
0answers
157 views

When is the final telephone post installed? [closed]

The puzzle is as follows: The Philadelphia telephone company will install 35 telephone poles along Broad Street. Each post must be located at equal distances from each other. It is known that the ...
1
vote
4answers
135 views

I need some help with this 15x15 nonogram

I have been working on this nonogram for some time and can't seen to figure out what to do next... This is the link: https://nonograms-katana.com/play/#game
5
votes
1answer
218 views

How to get the least possible sum in a closed loop set of squares?

The puzzle is as follows: The figure from below represents a set of 12 squares joined forming a closed loop. By using only the numbers from 1 to 12 fill in the blanks. The condition is that, without ...
8
votes
1answer
191 views

Nurikabe: The Terrible Tower of Threes!

This puzzle is a quick and fun little Nurikabe that is very tall, because I am not. It's not particularly tough, but if you need a nice relaxing grid-deduction puzzle to calm your brain today, this ...
-1
votes
2answers
110 views

How to find the least number of extractions to make the word QATAR?

The riddle is as follows: A local library has lended its catalog card cabinet so it can be used in a raffle. The raffle prize is a luxurious travel to the Middle East for vacations to an employee ...
3
votes
2answers
486 views

Matches to move in order to get right roman numeral over fifty

The riddle is as follows: The figure from below represents a set of roman numerals wrote in such a way that the sum is not correct. The numbers are arranged as: 50+12=51 How many matches minimum ...
-2
votes
2answers
105 views

How many have to enter the building so their birthday matches?

The riddle is as follows: Looking at his watch a doorman from an hotel in New York notices that 280 people are inside. Suddenly he begins to ponder the following. How many people should have to come ...
3
votes
1answer
137 views

Seven letters riddle

Hoping it is a never-seen riddle, here is the problem. We have seven letters A,B,C,D,E,F,G. Each letter is associated with a unique number between 1 and 10. We know the following: D is 3 units ...
0
votes
0answers
116 views

7x7 Skyscraper with clues and prefilled skyscrapers - next steps? [closed]

It's me again. I have another skyscraper issue. My program is now able to solve all the skyscrapers with sizes up to 8x8 and beyond. The only time it cannot calculate the complete solution is with 7x7 ...
1
vote
1answer
109 views

Number crossword puzzle

I'm trying to solve the following quiz from my daily quiz calendar (I have it in paper so I cannot give a link). It's like a crossword puzzle but with numbers. The empty cells should be filled with ...
6
votes
1answer
178 views

Fillomino with Sums: The Fillo That Smiles Back!

This puzzle is a Fillomino, with the special variant rule of Sums ("Cages") being applied. You might also notice that this particular fillomino is giving you a smile! This is my first time ...
8
votes
1answer
355 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 ...
9
votes
3answers
387 views

We have captured 5 spies. Their names are A, B, C, D, and E

This is a variant of the puzzle here. We have captured 5 spies belonging to a secret organization. Their identities are unknown; we only know them by their codenames A, B, C, D, and E. After thorough ...
18
votes
1answer
488 views

Bar trivia is heating up

An entry in Fortnightly Topic Challenge #49: Pub Quiz Camouflage Last week I popped into my local bar, Staggers, on Tuesday night with my work colleagues to have a few well drinks and jalapeño ...
5
votes
1answer
187 views

Double Ducky (or Fu-two-shiki)

There are two* logical, discrete ways to solve this Futoshiki puzzle, each with its own unique solution. You can solve it using the letters given, or use the numbers 1-5, but if you map the letters to ...
6
votes
0answers
133 views

Decoding a mystery sequence of falling boulders

I'm trying to unravel the algorithm for an old 1980s game called Wanderer. The game is a simple grid: 16 cells high (all visible in the image) and 40 cells wide (though not all are depicted). In the ...
0
votes
1answer
94 views

Skyscraper 6x6 - unable to get next step

I tried to write a program to solve a Skyscrapers puzzle. Currently I'm teaching it to find the next steps out of nopes (values which cannot be present on the field) values and clues. So far the field ...
3
votes
2answers
384 views

3 x 2 sliding puzzle

Would it be possible to solve a sliding puzzle like this (x is the space)?: 1 3 2 4 5 x I haven't been able to solve this and I don't even know if it's ...
14
votes
2answers
591 views

Now you're Packing with Portals #2: Hashtag

Place the colored shapes into the white area, without rotations or reflections, so that they fill it perfectly. The gray walls don't just block shapes, though - they act as portals! When you place a ...
-2
votes
1answer
91 views

Is asking your one question by doing an action an answer to the two doors, two guards puzzle? [closed]

Is asking your one question while doing an action an answer to the two doors, two guards puzzle? Example: You ask your one question by moving towards any door. Only the true guard will continue to ...
3
votes
2answers
129 views

What is the house number in nolteight street

Alice moved to nolteight street. Bob meets her after her move, and he knows that the smallest house number in nolteight street is 8, and the highest number is 100. But he does not know Alice's house ...
7
votes
1answer
149 views

Nurikabe: Five Below

This puzzle is another one of my Nurikabes, and this time it's a smaller one made entirely of pieces that are 5 or less. Perhaps you can tell that making puzzles in this genre is slowly becoming my ...
5
votes
1answer
445 views

Skyscrapers 6x6 - Stuck at the end

I tried to write a program to solve a Skyscrapers puzzle. Until the last steps I always used the opposite clues. But I can't find a solution for the last cells. This is where I am: ...
42
votes
2answers
2k views

Now You're Packing with Portals #1

I was staring at my window last night, and daydreaming (nightdreaming?) about filling it with shapes. Suddenly, I was struck with inspiration for a new type of puzzle! Here's a fairly easy instance: ...
14
votes
1answer
445 views

Pento-Doku: Pentominous + Sudoku

Intended for Fortnightly Topic Challenge #47: Wacky Sudokus, but I was too slow making it... not for lack of trying, I assure you This puzzle is both* a Pentominous and a Sudoku**. Rules Solve the ...
3
votes
1answer
87 views

A Final Digitial Sudoku! - SS#14

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the final puzzle in this series! For more information about the series, see the first ...
12
votes
2answers
566 views

Unequal Curfew - Donut Hole

This is a Curfew variant. Curfew is a genre invented by Hempuli; I made a slight modification to give this variant. Rules of Unequal Curfew: Draw a loop that visits every circle. Each visit to a room ...
15
votes
1answer
436 views

This Sudoku Park iS LIT!

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" The grid below is a normal Sudoku grid with normal Sudoku clues, but the completed grid also houses a Statue Park! The completed ...
12
votes
1answer
290 views

Sudoku: Odd Bonds

An entry in Fortnightly Topic Challenge #47: Wacky Sudokus. Edit: Clarified three of the rules. Rules: Normal sudoku rules apply. Inside the sudoku, there exists one "loop". The loop ...
9
votes
1answer
234 views

A Fractal Sudoku - SS#13

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the penultimate puzzle in this series! For more information about the series, see the ...
6
votes
1answer
177 views

Logic grid puzzle - Carson City Chronicle

I can't figure this one out. Any help would be appreciated. Journalist-in-training Janet Seymour's byline appeared in the Carson City Chronicle on six days last week. On each day (Monday through ...
9
votes
1answer
456 views

Sudoku with no grid and no numbers!!? - SS#12

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the twelfth puzzle in this series! For more information about the series, see the first ...
20
votes
1answer
957 views

Sudoku in Technicolor!

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" This puzzle consists of three overlapping Sudokus, coloured red, blue and green, so each cell will contain three digits, one of ...
15
votes
2answers
2k views

Hotaru Beam Puzzle: Is it impossible?

I saw this puzzle on Twitter by user @lilva_0419 and I personally feel that it is impossible to solve. Can you prove me wrong (or right)? Source on Twitter Try it online Rules (see Wikipedia): ...
7
votes
1answer
666 views

Finding the median of 5 numbers

There are 5 boxes labeled A, B, C, D and E. Each box contains a distinct number, but you don't know what it is. You can select three boxes and the Oracle will tell you which box contains the median* ...
6
votes
3answers
557 views

Table of mathematical expressions - fill in 1-9

Fill in the numbers 1 through 9 in the 9 empty cells (each number appears exactly once) to make the row and column expressions equal to the number at the end of the row or column. Regular math ...
7
votes
1answer
102 views

This Sudoku takes a step up! - SS#11

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the eleventh puzzle in this series! For more information about the series, see the first ...
37
votes
1answer
1k views

Didn't you ask me for a crossword?

An entry in Fortnightly Topic Challenge #forty-seven: "Wacky Sudokus" Here's that crossword you asked for... Sorry, what's that - you didn't ask me for a crossword?? TASK: Solve the puzzle ...
12
votes
1answer
401 views

Skyscrapers in Sudoku!!! - SS#10

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the tenth puzzle in this series! For more information about the series, see the first ...
14
votes
1answer
491 views

Chain Puzzle: Video Games #01 - Teleporting Crosswords!

This is the first Chain Puzzle in the Video Games series, in which all puzzles are themed around video games of all genres. The answer to this puzzle is a thematic word or phrase. The solver whose ...
26
votes
1answer
1k views

A Puzzling Sudoku (Warning: Hot!)

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" A Sudoku with an oddly familiar shape. Here's a Penpa Link. Rules: Normal Sudoku rules apply (Special) Thermometers: The ...
9
votes
1answer
306 views

A 7x7 Suguru - SS#9

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the ninth puzzle in this series! For more information about the series, see the first ...
10
votes
1answer
368 views

Nurikabe: The Super-Kabe Attacks!

This puzzle is another Nurikabe, but with a new twist for me: it's a gigantic Super-Kabe! It's also, in my opinion, quite tricky and has some interesting deductions. I hope you enjoy! Rules of a ...
25
votes
1answer
1k views

The Blank Sudoku

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" (h/t to Beastly Gerbil, whose 1,2,3... Trinary!!! puzzle provided inspiration for this puzzle) This puzzle is a normal Sudoku, ...

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