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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4
votes
0answers
19 views

A Difficult Wacky Sudoku - SS#8

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the eighth puzzle in this series! For more information about the series, see the first ...
11
votes
1answer
177 views

A Scrumptious Sudoku Sandwich - SS#7

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

Sudoku… with 10 digits? SS#6

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

Compoundoku wants REALLY BIG and WACKY!

This is an entry for Fortnightly Topic Challenge #47: Wacky Sudokus. Rules of Compoundoku: Solve both left and right Sudokus. In addition, the board below them is the Compound Board of both Sudokus. ...
10
votes
1answer
278 views

Nurikabe: The Twisty Corridors

This puzzle is a Nurikabe. It is a little tougher than my previous one, which was designed for newer solvers, and it has a particularly squiggly solution that I found pleasing enough to post - hence ...
7
votes
1answer
103 views

A Mosaic Sudoku - SS#5

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the fifth puzzle in this series! For more information about the series, see the first ...
15
votes
1answer
865 views

Stop BorgBot before it's too late!

There was a deafening metallic thunk as the rogue AI locked the door of the PuzzlingCorp server room, trapping the engineers inside. A countdown appeared on the computer screen... and began counting ...
9
votes
1answer
424 views

Consecutive integers with digit sum divisible by 19

What is the smallest positive integer N, such that the digit sum of N and N+1 are both divisible by 19?
3
votes
1answer
77 views

Sudoku + Nurikabe = Sudokabe

The following Sudoku has a nice little twist: after solving, use the numbers in the green squares as a basis for a Nurikabe puzzle. You can create a new grid for the Nurikabe (a 9x9 grid with the ...
13
votes
1answer
169 views

This is an Odd Sudoku - SS#4

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the fourth puzzle in this series! For more information about the series, see the first ...
11
votes
1answer
160 views

Greener Grasses: Nusi's Birthday

Here is another Greener Grasses puzzle. Also, happy happy birthday to my fellow Indonesian puzzler, Nusi! I'm sorry that I realize the puzzle was broken in the last-minute checking so a single letter ...
-2
votes
2answers
147 views

How many children wear a yellow t-shirt?

The puzzle is as follows: In a certain kindergarten there are 23 children. Some of them wear a green t-shirt, others a yellow t-shirt and others blue t-shirt. A tv reporter who was on the site doing ...
7
votes
1answer
109 views

Shattered Webs - SS#3

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the third puzzle in this series! For more information about the series, see the first ...
10
votes
2answers
286 views

1, 2, 3… Trinary!!! (SS#2)

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the second puzzle in this suduko series! For more information about the series, see the ...
16
votes
0answers
177 views

Stupendous Sponge

General Notes This puzzle takes the form a 9×9×9 level-one Menger sponge whose surface is divided into 648 1×1 cells. The aim is to draw a single non-crossing loop along its surface by connecting the ...
4
votes
6answers
949 views

How many children have two colored flags?

The puzzle is as follows: A classroom in kindergarten has 35 children. Each of them carry a flag of one, two or three colors. The number of only two-colored flags is double that of the monochrome ...
13
votes
1answer
424 views

The Blind Killer - a new series! SS#1

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to a new sudoku series! This series will run for the duration of the current Fortnightly ...
9
votes
1answer
174 views

Familiar Five (r&r ignored)

What is the correct option/answer to this puzzle?
0
votes
1answer
130 views

How do you find the average score in an archery competition?

The problem is as follows: In an archery contest the television host says the following: The scores in this round of competition are from 0 to 20. Charles has 2 points less than Marina. Lewis has 2 ...
0
votes
2answers
151 views

How old is Brenda?

Five friends (Adele, Brenda, Carol, Dana and Emily) were born peculiarly in consecutive years. It is known from their diaries that: Carol was born 2 years before Dana and is not the oldest of them all....
1
vote
0answers
75 views

100 boxes, only 50 attempts [duplicate]

There are 100 boxes in the room. In every box there is a note with some number from 1 to 100 (no repetitions).Person A comes into the room and checks all the boxes and notes inside them. He can (doesn'...
20
votes
1answer
527 views

2021 Unpainted Masyu

Paint some white circles to black such that the Masyu will be uniquely solvable and: Exactly 2 of 11 white circles on the left forming '2' should be painted black. Exactly 0 of 12 white circles on ...
-6
votes
1answer
74 views

Landings and stairs [closed]

Let's have two views of landings and stairs. We obtain the second VIEW B, by rotating the VIEW A 180 degrees clockwise. The distance between two landings is 8 feet, shown by the arrows. The stairs are ...
-8
votes
1answer
126 views

Shikakui Hebi: Similarities

Introduction puzzle: here So, my first Shikakui Hebi puzzle didn't go well, so I'm trying again! Only this time, no more arrows. Instead, it's now a nonogram-like! This is a Shikakui Hebi puzzle. ...
8
votes
1answer
142 views

Sashi Park: an introduction

This is a Sashigane-Statue Park hybrid. The rules might look complicated, but they're just the two rulesets smushed together. Familiarity with both genres will help. Rules Statue Park (adapted from ...
0
votes
1answer
105 views

Books on a bookshelf

On a shelf the blue book is to the right of the red book, the yellow book is in one end, the black book is just before the white and the green is between blue and white. What is the order of the green ...
-1
votes
1answer
168 views

Password with capital letters

John created a password for a social network, thinking he could forget it, he left the information below in his agenda: None of the syllables is in the word JUCOMAGO: Two syllables are in the word ...
5
votes
2answers
487 views

Nine neighbors in a hotel

Alessandra, Marta, Cristiane, Camila, Eduardo, Janice, Giulia, Mateus and Lucas are neighbors who live in a hotel. On each floor there are three bedrooms: one on the left, one in the center and one ...
9
votes
1answer
144 views

Tetrikabe: Parallelogram

Rules: (Nurikabe section shamelessly stolen from an earlier puzzle by @jafe) Numbered cells are unshaded. Unshaded cells are divided into regions, all of which contain exactly one number. The number ...
0
votes
0answers
59 views

Hundred prisoners [duplicate]

I got a puzzle that I can't figure out. A hundred prisoners are waiting to be executed. The warden comes to them with an offer. He will give each one of them a secret number, from 1 to 100, not all ...
5
votes
2answers
200 views

A square in the plane with 4 vertices of the same color

Every point in the plane is colored either red or blue. Is it necessarily the case (i.e., is it true for all such colorings) that there exist some four points of the same color that are the vertices ...
13
votes
1answer
199 views

Nurikabe: A Gentle Walk in the Hall of Giants

This puzzle is a Nurikabe that is designed to be a gentle introduction to the genre, with a learning curve of progressively harder deductions. It is encouraged for first-time solvers and those who ...
5
votes
3answers
175 views

Who took Gwen's purse and jacket?

The puzzle is as follows: Four sisters went to the movie theater. While leaving the venue each one of them took by mistake the purse of another sister and the coat of another different sister. Maria ...
1
vote
1answer
144 views

Ohh, NSA Again? #2

This puzzle is the second part of story Ohh, NSA again?. Hope like this story. Here it is: John got the target, it was Stack. Problem is, it can be Stack Overflow or Stack Exchange. Another problem ...
1
vote
1answer
95 views

Three doors, three locks [closed]

Can you help me with this puzzle? A person is trapped in a room that has 3 locked doors and there are three colored keys: red, yellow, and green. He was provided the following information: Each of ...
4
votes
1answer
172 views

Einstein's Puzzle with 5 furniture customers

Einstein had made quite a good zebra puzzle tough enough to confuse many people's brains. Today I present even tougher one, will you be able to solve it? There are 5 customers, who bought a different ...
-1
votes
1answer
177 views

Shikakui Hebi: Introduction

Shikakui Hebi is a new grid deduction puzzle I invented. It translates from Japanese which means "Square Snake". It quite sounds like Slitherlink, but trust me, it isn't. Rules of Shikakui ...
-3
votes
2answers
195 views

Kyudoku :- Merry Christmas?

Previous Puzzle:- Kyudoku :- Introduction There will be numbers in a grid. You just have to circle nine unique numbers (1 to 9) such that each row and column has sum of 9 or less. In some puzzles, one ...
11
votes
1answer
352 views

Cheesemonger's puzzle

An entry in Fortnightly Topic Challenge #45: Flags The cheesemonger wants to arrange the wheels of cheese on display. The display case has two shelves with space for three wheels of cheese on each. He ...
11
votes
2answers
603 views

Kyudoku :- Introduction

This is a Kyudoku Puzzle. I have made the rules myself. There will be numbers in a grid. You just have to circle nine unique numbers (1 to 9) such that each row and column has sum of 9 or less. In ...
6
votes
1answer
256 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 ...
9
votes
1answer
205 views

Embassy Park - A Grid Deduction Puzzle

An entry in Fortnightly Topic Challenge #45: Flags This grid deduction puzzle is a variation on the OP's previous Office Park puzzle. You are given a set of seven buildings, which are tetracubes, 3-...
8
votes
2answers
400 views

Sounds beautiful, doesn't it

So I found this puzzle from an old book of mine with very little instructions. I can't seem to remember the right approach to the solution BUT I do remember the final answer, which is 8 letters only. ...
10
votes
1answer
183 views

Easy As LITS: Lots of “S”s

This is an Easy as LITS puzzle (LITS variation), where you shade cells to form tetrominoes Rules taken from Grandmaster Puzzles: Shade exactly four connected cells in each outlined region, to form an ...
12
votes
1answer
732 views

If 2020 Were A Sudoku

A bit of light relief to round out the year. No special genius required :-)
4
votes
1answer
97 views

Did you go inside, or…?

The following underscores represent the letters in a sentence. There are extra spaces between some, indicating a word delimiter. Punctuation is included in the sentence. ...
12
votes
2answers
289 views

A sudoku that's already filled in for you

The usual rules of sudoku apply: each row and column must have one of each digit; plus, if you divide the whole nine-by-nine grid into nine three-by-three subgrids, then each subgrid has one of each ...
10
votes
1answer
205 views

Hokuro Puzzle 10x10

After introducing this new puzzle type, here is a slightly more challenging Hokuro puzzle. Hokuro is a grid deduction puzzle inspired by Kakuro with the following rules: Each cell contains one of the ...
29
votes
1answer
808 views

A flag-packing problem

An entry in Fortnightly Topic Challenge #45: Flags You are provided with a 9x9 grid of squares and 21 minimalistic flags (pictured below, all shown to scale). TASK: Assign a colour (Black, Blue, ...
10
votes
1answer
202 views

Sashigane: 5 arrows + 1 six

This is a Sashigane puzzle, where you divide the grid into L shapes. Rules taken from Nikoli: Divide the grid into L shaped blocks - one block wide. All blocks must be L shaped. Cells with open ...

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