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).
2,104
questions
-1
votes
1answer
41 views
Figure out the next two numbers in this sequence [duplicate]
1,11,21,1211,111221,312211,13112221,1113213211,....?
Find the next two numbers in the sequence
This question appeared in my math competition and I managed to solve it, and I will give a hint if ...
7
votes
1answer
177 views
Can you solve this football league table problem?
Each team (A,B,C,D,E,F) plays each other once (on a neutral ground). Maximum number of goals scorable is 4. A team gets $3$ points for a win, $1$ point for a draw and $0$ points for a loss.
At the ...
2
votes
2answers
163 views
Guess the numbers
One day Bob and Alice walk around they were having the following conversation:
Bob: Alice go ahead and pick any random number.
Alice: Okay, I have one.
Bob: Alice multiply the random ...
5
votes
2answers
134 views
Is “meta”-logic valid for solving puzzles? [duplicate]
I think this question is best explained with a demonstration. In this case I'm playing a Range puzzle, but this kind of concept seems to work with other puzzle types too.
Of interest here are the two ...
14
votes
3answers
1k views
A King's Hamiltonian Tours
a) Place the numbers 1 to 25 in the cells of a 5 x 5 board in such a way that consecutive numbers occur in adjacent cells either vertically, horizontally, or diagonally, and so do cells with numbers 1 ...
5
votes
1answer
151 views
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....
3
votes
2answers
126 views
The Mixed-Up Label [duplicate]
Mrs. Hudson had a rather large number of her extended family over for tea, and during this time a particularly mischievous great-nephew took the opportunity to wreak havoc in the kitchen. Seeing that ...
10
votes
1answer
227 views
Double Chocolate: Happy Valentine's Day!
Hikouki (@flight_float) over on Twitter issued a challenge to make a Double Chocolate logic puzzle with a fixed grid pattern, and lots of logic puzzle makers responded to that challenge! Here's my ...
17
votes
1answer
545 views
On The Subject of Blind Alleys
(This is part of a series of puzzles written for Timwi for a Secret Santa puzzle exchange, themed around various custom modules for the game Keep Talking and Nobody Explodes. No KTaNE knowledge is ...
17
votes
7answers
3k views
When was Alice Born?
This is inspired by the following recent question: Living next door to Alice
Having failed to figure out where Alice lives, Bob and Charlie endeavour to determine the month in which Alice was born. ...
11
votes
1answer
776 views
Welcome to the club
A financial manager of a bowling club, whose members are all couples (a man and a woman), creates three different membership lists.
In the first list the couples are sorted by increasing age of the ...
11
votes
3answers
902 views
The Troll, the dwarves and the gloves
A group of $N$ dwarves are caught by an evil Troll. As usual the Troll gives the dwarves a chance to escape if they solve a puzzle he created just for the occasion.
Tomorrow morning each dwarf will ...
22
votes
1answer
873 views
Using burning ropes as timer - how to measure 1 hour and 8 minutes with 3 ropes?
This is a variation of a well known puzzle, you can find the other versions on PSE.
You have three ropes and a box with ten matches.
As usual each rope takes one hour to burn completely when lighted ...
18
votes
1answer
404 views
A special soccer tournament
30 soccer teams participate in a tournament. Each team plays against every other team exactly once.
For a victory a team gets 2 points, for a draw 1 point and for a defeat 0 points.
At the end of the ...
13
votes
1answer
248 views
Lenny’s Logical Internship
Lenny recently applied for an internship at Logicorp™, a company built around using logical reasoning to solve any sort of problems their clients face. The interview was long and difficult, and Lenny ...
33
votes
7answers
6k views
Living next door to Alice
Bob and Charlie live in a small village with 99 houses, numbered from 1 to 99.
One day they meet Alice, a person who has recently moved to this village.
Bob asks her if her house number is a square ...
9
votes
2answers
452 views
Setka - Complete grid using clues and sudoku-style logic; Theme - Halftime
This is a Setka puzzle; you can find more (along with a more detailed explanation of the rules) at our website, linked from our profile.
How to play Setka, the short version:
Answer each clue using ...
-3
votes
1answer
171 views
How many ways could Alice have filled out the answer sheet? [closed]
Alice, Brie, Carlos, and Drake are taking a true/false quiz at school. There are four questions.
The teacher was sneaky and made the answer to every question "true." Each person got a
different score, ...
15
votes
1answer
272 views
Missing No. 53 - Act 1: A Musty House
2/10/2020
Agent: Delta Flash
Subject: William Plixer
Age: 37
Gender: Male
Appearance: Crew cut hazelnut hair. Round, blue eyes, snub nose, attached earlobes, and thin lips on ...
20
votes
1answer
802 views
Unbalanced weight of boxes
You are given a traditional balance scale with two pans (no reading) and 6 boxes with the following properties:
1) the weight of each box is a positive integer number
2) if you put any number of boxes ...
13
votes
3answers
710 views
Find a number based on lies about divisibility
A teacher writes a positive integer n < 50000 on the blackboard.
The first student claims, that n is divisible by 2.
The second student claims, that n is divisible by 3.
The third student claims, ...
9
votes
1answer
369 views
99 numbers on the blackboard
The numbers 1,2,3, ..., 99 are written on the blackboard. Alice and Bob play the following game, taking turns. Alice starts.
At every turn, each player removes one number until two numbers are ...
4
votes
3answers
277 views
Two shapes that cover a 4x4 grid with any 1x2 missing
Can you find two geometrical shapes with the following property: If you remove any 1x2 rectangle from a 4x4 grid, then the remaining area can be exactly covered with the two shapes. What do these two ...
8
votes
1answer
235 views
Constructing an island according to rules in Smullyan's “What is the Name of this Book”
I've recently finished dropping my jaw at Raymond Smullyan's "What is the Name of this Book," and the section on Gödel's incompleteness theorem, involving islands of knights (truthers) and knaves (...
5
votes
1answer
148 views
Setka - Complete grid using clues and sudoku-style logic
This is a Setka puzzle; you can find more (along with a more detailed explanation of the rules) at our website, linked from this user's profile.
How to play Setka, the short version:
Answer each ...
10
votes
3answers
329 views
Wizard's Labyrinth
A thief has snuck his way into the wizard's castle. After traversing a plethora of magical traps and illusory walls, he finally spies the wizard's hidden stash of gems beyond the end of a long ...
43
votes
3answers
5k views
Cover 63 squares of a chess board
Can you find 3 similar geometrical figures (common shape but can be different sizes) A, B and C with the following property:
If you remove any square from a 8x8 chess board, then the remaining area ...
10
votes
1answer
613 views
Three shy fairies performing two thousand times
Three shy fairies participate in a dance competition. Since they are shy they don't want to be seen by anyone except for the five judges of the competition. The competition is composed of $2000$ ...
8
votes
1answer
595 views
One piece of a destroyed chess board
Once I met a friend and he told me the following story:
I recently cut my wooden 8x8 chess board into different rectangular pieces along the edges.
Each square of the chess board has a length of one ...
0
votes
1answer
193 views
Circular arrangement with professions and age based puzzle [closed]
Eight people, named A, B, C, D, E, F, G, and H; who work as a dancer, singer, lawyer, painter, doctor, teacher, architect, and professor; are 25, 40, 45, 29, 66, 24, 21, and 34 years old; although ...
28
votes
1answer
1k views
This new puzzle type needs a name {3}
I believe I have invented** a new type of puzzle...
What is its name?
** Well, 'adapted' an existing one, really...
Colour-blind-friendly version available here. Those without colour-blindness ...
11
votes
2answers
518 views
Compoundoku wants BIG
Rules of Compoundoku:
Solve both left and right Sudokus.
In addition, the board below them is the Compound Board of both Sudokus.
Each number on the Compound Board should tell either: (1) ...
8
votes
2answers
297 views
Can you open a safe with a lengthy complicated combination?
Two cousins were talking about their parents' safes. "They said I can keep my comic books in their safe, if I figure out the right combination, and enter it on the keypad correctly on my first ...
7
votes
1answer
270 views
wandering knight
Suppose a land with a finite number of castles. Each castle is connected (via roads) with exactly 3 other castles.
One knight leaves from his castle and starts travelling. He moves in the following ...
23
votes
2answers
1k views
Introducing: Compoundoku!
Rules of Compoundoku:
Solve both left and right Sudokus.
In addition, the board below them is the Compound Board of both Sudokus.
Each number on the Compound Board should tell either: (1) ...
1
vote
1answer
234 views
What is the maximum number of allies that you can have in this scenario?
There is a military/diplomatic crisis, with many sides involved. Your goal, as an uninvolved party now entering the conflict, is to get as many allies as you can. You make an ally by supporting a ...
3
votes
2answers
115 views
How to effectively hide an earth rebooter thingy [The Good Place Season 4 spoilers]
This puzzle is unsolved. I don't know if there is a solution or how to solve it. I'm also not sure what type of puzzle this would be, so if anyone wants to correct the tags, feel free.
Imagine you ...
0
votes
0answers
198 views
A Logician's Game of UNO Flip
Two players are in the middle of an ongoing one-on-one game of UNO Flip, with all its standard rules in effect.
Play is currently Light Side Up. It is Player B's turn. Player A has 3 cards remaining, ...
0
votes
0answers
68 views
The king, the princess, the 3 wise men, and the 3 x's [duplicate]
A princess just became of marriageable age, and her father went out to get 3 wise men. He placed them at a round table and wrote either an X or an O on each of their heads, writing in such a way that ...
11
votes
1answer
416 views
Latin-Square Adjacent Puzzles
Here are two $5 \times 5$ Latin-Square Adjacent puzzles. For each cell, put a digit between $1$ and $5$ such that:
Each row and column contains one occurrence of each digit $1$ to $5$.
If two cells ...
-1
votes
1answer
166 views
The Death Recording
A woman was found dead in her house. She lay slumped on her desk, holding a gun in her hand. A cassette tape recorder was on her table. The police on entering the house saw the cassette recorder and ...
6
votes
2answers
228 views
The Train and The Cyclist [closed]
A railway track runs parallel to a road until a bend brings the road to a level crossing. A cyclist rides to work along the road everyday at a constant speed of 12 miles per hour.
He normally meets ...
9
votes
9answers
2k views
Find two coins using a balance scale
You are given 20 identical coins. 18 of those coins have a weight of 10g each, 1 coin has 9g and 1 coin has 11g.
You are given a traditional balance scale with two pans (no reading).
What is the ...
2
votes
6answers
1k views
2 crates and 2 logicians
Two perfect logicians (A and B) each have a bag of gold coins.
A has more coins than B and each bag contains an amount of coins which is some multiple of 6. All coins are identical in appearance and ...
6
votes
1answer
290 views
Density-type puzzle: Having A Good Day?
Here's another Density puzzle. I've got to say, I really like making these. Part of this is pretty simple, and part of it is much more complicated. Let's see what happens! Here it is:
Solution: (3,1,...
1
vote
1answer
162 views
The Tower Password [duplicate]
A thief plans to break into a castle, but unfortunately, it is surrounded by a moat that the thief cannot possible swim through. The only way they can hope to get in is through the main entrance, ...
7
votes
2answers
466 views
Pensive Nonogram - Two-Colour Puzzle
Fourth two-colour puzzle in the 32nd issue of Mega Pixel Puzzles by Puzzler.. I’ve made some progress, but I am stuck. Can you help me find my next move in it? (The puzzle is below)
13
votes
4answers
1k views
Reconstructing the results of a 6-team soccer tournament
6 teams played in a "round-robin" soccer tournament, in which each team played each other team once. Each game had 3 possible outcomes: team 1 won, draw, or team 2 won. The winning team received 3 ...
14
votes
1answer
763 views
Reconstructing the results of a 5-team soccer tournament
5 teams are playing in a "round-robin" soccer tournament, in which each team plays each other team once. Each game has 3 possible outcomes: team 1 wins, draw, or team 2 wins. The winning team receives ...
