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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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
474 views

Pentopia: One-way Crossing

This is an entry for Fortnightly Topic Challenge #44: Introduce a new grid deduction genre to the community. Here is a standard Pentopia puzzle. Rules of Pentopia: Place some pentominoes into the ...
14
votes
1answer
514 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
329 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
392 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, ...
11
votes
1answer
496 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 ...
2
votes
1answer
415 views

What will be the price of the dog? [closed]

Two men had a certain number of camels, and sold those camels. The price of each camel was equal to the total number of camels they owned initially. They then bought a certain number of goats for that ...
12
votes
1answer
254 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 ...
19
votes
1answer
288 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. ...
11
votes
1answer
313 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
618 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 ...
7
votes
1answer
187 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 ...
10
votes
1answer
340 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 ...
-4
votes
6answers
660 views

Somebody ordered a pizza

Somebody ordered a pizza. They ordered X slices with pepperoni, Y slices with mushrooms, and Z slices with cheese. If no two slices were identical, and no combinations of toppings were not present, ...
15
votes
1answer
949 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
437 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?
-2
votes
2answers
181 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 ...
3
votes
1answer
139 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 ...
11
votes
1answer
193 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 ...
14
votes
1answer
237 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 ...
5
votes
2answers
559 views

It's a Vote! Everybody Out!

There is a country ruled by a ruthless Emperor. He has a plan to make people miserable by ridding himself of the most popular members of the population. Every month, each person in the population has ...
9
votes
1answer
165 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 ...
0
votes
2answers
187 views

Find the competition rankings of three people based on their final scores

I found this puzzle in my Logic and Reason book from 2000's. The topic is ordering information. From the looks of it seems to be an adaptation from a reprinted version of Martin Gardner's 70's book of ...
10
votes
2answers
406 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 ...
3
votes
6answers
983 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 ...
21
votes
2answers
1k views

Masyu jigsaw puzzle

Here's a masyu puzzle for you. The rules are as follows Draw a single closed loop which does not cross or touch itself. The sections of the loop run horizontally or vertically between the ...
9
votes
1answer
200 views

Familiar Five (r&r ignored)

What is the correct option/answer to this puzzle?
5
votes
3answers
12k views

How do I reduce a negative hint with multiple possibilities?

This is a hypothetical question about grid-style logic puzzles. I know that when there are positive clues, you reduce the puzzle by eliminating possibilities that don't come in pairs; for example, if ...
0
votes
1answer
137 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 ...
16
votes
2answers
4k views

Is it indeed impossible to score any points in the test in Heinlein's “Space Cadet”?

In Heinlein's Space Cadet, one of many tests administered to the protagonist seems to have no way of scoring any points. See the excerpt below. Late in the day he was ushered into a cubbyhole ...
35
votes
3answers
5k views

Pirates and gold coins

A group of N pirates has come by a chest containing 200 gold coins. Their rules require that the coins be distributed by the following approach. The pirates are ranked from fiercest to meekest and ...
1
vote
0answers
77 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
548 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
82 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 ...
23
votes
3answers
3k views

Winning an unfair game

I came across the following interesting problem today: A game consists of a sequence of plays; on each play either you or your opponent scores a point, you with probability 𝑝 < 1/2, he with ...
-10
votes
1answer
174 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. ...
0
votes
1answer
117 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 ...
9
votes
5answers
502k views

Puzzle of putting numbers 1-9 in 3x3 Grid to add up to 15

In a 3x3 grid, I'd have to put numbers from 1 to 9 in a manner so that respective row, column and diagonal add up to 15. I have only been able to come up with one solution: 6 1 8 7 5 3 2 9 4 ...
8
votes
1answer
167 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 ...
5
votes
2answers
596 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 ...
-1
votes
1answer
178 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 ...
40
votes
3answers
2k views

Animal Cross(word)ing

An entry in Fortnightly Topic Challenge #43: Variety Crossword Grids Each of the 40 clues listed below (a mix of pop culture and science/nature) yields the name of an animal. Your task is to solve ...
15
votes
2answers
2k views

How many pirates were there, and how much was the booty?

A pirate crew at the end of the day split the booty. The first pirate got 100 gold pieces and 1/6 of the remaining booty. The second one got 200 gold pieces and 1/6 of the remaining booty. The third ...
8
votes
1answer
160 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 ...
2
votes
1answer
139 views

Nurikolor (Level 9)

Previous Level: Nurikolor (Level 8) It's been almost two months since I've last done this. Don't worry, I'm not dead, I was just working on this. RULES: There are colored numbers on the grid, which ...
13
votes
1answer
297 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 ...
11
votes
1answer
835 views

Weird and complex puzzle that we need help with

So basically this is a complex deep web puzzle and we're pretty much stuck at it right now as we don't have any idea what this is about, any help will be aprreciated (the attached images are the ...
4
votes
3answers
192 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 ...

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