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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-1
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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
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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
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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
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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
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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
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1answer
151 views

Just Another Sudoku for PSE

Crafted with love for PSE, <3
17
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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 ...
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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
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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
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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
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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
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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
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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
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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
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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
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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 ...

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