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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9
votes
1answer
232 views

Akari: The Light

Rules (taken from Nikoli): Place light bulbs (circles) according to the following rules. Light bulbs may be placed in any of the white squares, the number in the square shows how many light ...
4
votes
2answers
134 views

How can I make a valid conclusion about a set of statements which are in tandem?

The problem is as follows: If there are no government subsidies for agriculture, then there are government controls on agriculture. If there are government controls on agriculture, then there ...
1
vote
0answers
181 views

Math tapestry puzzle #3

Continuation from Math tapestry puzzle #2 Now things are heating up, it looks like this is slowly becoming bigger. I saw my friend Anna working on her tapestry. She asks me, "Do you like it?" ...
32
votes
1answer
1k views

This cipher needs a name!

This puzzle is a spin-off from the 'This new puzzle type needs a name' series. I have devised a new cipher and used it to encode its own name. I need you to tell me: What is its name? This puzzle ...
0
votes
1answer
118 views

Math tapestry puzzle #2

This continues from Math tapestry puzzle #1. Find the rules there. Continuing on from that, I saw my friend Jason come outside. We had a conversation about the things that are here. Suddenly he says: ...
1
vote
1answer
89 views

How can I find which sport/hobby corresponds to which friend when a set of given clues is provided?

Marina, Mike, Roger, Phillip and Justin has each only one hobby from the following list: motocross, badminton, swimming, athletics and karate, but not necessarily in that order. It is known that: ...
3
votes
2answers
131 views

How can I find which person belongs to a specific occupation when the clues involve degree of friendship or acquaintance?

The riddle is as follows: Brenda, Lara, Mie and Nancy have each one profession. These professions are, baker, graphics designer, photographer and cosmetologist. But not necessarily in that ...
3
votes
1answer
163 views

Fork in the road problem - with a single person

You walk to a fork from where two roads come out - one leading to a post office and the other to a university. You want to go to the university, but do not know which road would lead you to it. A ...
6
votes
1answer
141 views

Puzzle - Snow Day Event

Daisy, Delilah, Donny, and Duke have each decided to participate in the snowperson building event. In decorating their snowperson, each of them has chosen a different colour of the scarf from purple, ...
6
votes
3answers
229 views

A Game of Dice and Logic II

Part 1, same game rules, slightly different cards This question is broken - my program for proper analysis failed in some catastrophic way, and the question does not work as planned. The intended ...
2
votes
1answer
172 views

Math tapestry puzzle #1

I went outside. I saw several math tapestries. Apparently they mean something. What goes in spot NN? I know from my friend that... Two adjacent numbers always have the same sum. The 4 numbers in each ...
15
votes
5answers
1k views

A Game of Dice and Logic

A friend and I are playing a cooperative game. He has two D7 dice and 5 cards in front of him. They read; ...
7
votes
1answer
157 views

Guessing the coin flips [duplicate]

Two prisoners, Alice and Bob, are captured by a dragon and placed in separate, isolated cells. The dragon then flips an infinite number of fair coins, and tells the outcomes of odd throws to Alice and ...
12
votes
2answers
2k views

It's my sister's birthday

I'd ordered her a cake, but when I got to the bakery to pick it up, the cake decorator had transposed the digits of her age. "She'll thank you for the compliment," I said, "but her age is a prime ...
3
votes
0answers
96 views

Splitting a Grid in 4 Equal Portions [closed]

I was wondering if someone could provide a solution to this. Instructions are provided. Thank you.
7
votes
1answer
196 views

Two persons and one question “Is the shaman honest”. Which one of them is the shaman?

An anthropologist arrived to the shaman's den where there were two persons, one with a green hat and one with a blue hat. One of the shaman's students had said that there was a Star Predictor with the ...
6
votes
2answers
401 views

Puzzle - Counting Lights, Not Sheep

Some nights it is difficult to get to sleep. On one such night, John counted the number of LEDs (Light-Emitting Diodes) on his clock radio that was on to make each individual time from 10:00 PM to 12:...
1
vote
1answer
89 views

Setka - Complete grid using clues and sudoku-style logic; Theme - Greenwich Village Resident

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. Theme: Greenwich Village Resident How to play Setka, the ...
6
votes
1answer
146 views

Cryptic 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 ...
6
votes
2answers
396 views

Smullyan Logic Puzzle about Nelson Goodman Principle - Knights and Knaves

In Smullyan's "Logical Labyrinths" there is the following problem 1.11: ...
7
votes
1answer
168 views

Montague Island Mysteries Logic-Grid Puzzles

I'm working through the logic-grid puzzles in the book called "Montague Island Mysteries" by R. Wayne Schmittberger. The particular puzzle I'm on is Puzzle 5.3 where breakfast guests choose food ...
-1
votes
1answer
82 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 ...
8
votes
1answer
240 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
241 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
306 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
181 views

Just Another Sudoku for PSE

Crafted with love for PSE, <3
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....
10
votes
1answer
284 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
598 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 ...
19
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
797 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 ...
12
votes
3answers
998 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 ...
24
votes
1answer
946 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
435 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 ...
14
votes
1answer
301 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 ...
11
votes
2answers
477 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
189 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, ...
16
votes
1answer
326 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
834 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
737 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
403 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
318 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
263 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 (...
6
votes
1answer
166 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
353 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
639 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
624 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 ...

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