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
3answers
206 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 ...
34
votes
3answers
3k 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
574 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
562 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
187 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 ...
26
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
496 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
270 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
259 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
225 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
106 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
186 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
67 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 ...
8
votes
1answer
260 views

Is Every Obtuse Angle A Right Angle?

The Journal of Irreproducible Results once posted an article saying that every obtuse angle is a right angle. Their argument follows below: Given the obtuse angle $x$, we make a quadrilateral $ABCD$ ...
11
votes
1answer
402 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 ...
4
votes
3answers
225 views

Linking Cars on a Track going at Different Speeds

A kid places three model cars on a long, straight track equally spaced apart. He sets each of them to a different speed (though he forgot the specific speeds). These cars are special, though: they ...
7
votes
1answer
170 views

Removing a Point, then Adding Two Others

Start with a point on $(0,0)$ on a two-dimensional lattice. Every move, you must follow this rule: for a point $(m,n)$, if there are no points on $(m+1,n)$ or on $(m,n+1)$, then you can remove point $(...
-1
votes
1answer
151 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
219 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
279 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
154 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
460 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
759 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 ...
0
votes
0answers
76 views

A spy in Fruitland [duplicate]

The army of the big and violent-prone country of Fruitland is planning to launch a nuclear rocket that could possibly destroy the near pacific little country of Vegetablesland. It is well known that ...
4
votes
1answer
169 views

A Coldport Christmas puzzle

Detective Inspector Playfair, an energetically boisterous policeman who often complained about Endeavour Morse having his own TV show, was sat on a bench at the side of Coldport's newly laid town ...
4
votes
1answer
316 views

Using burning ropes as timers

This puzzle is an harder version of a very famous one. It has been asked many times on PSE, but this time the question is slightly different (1) (2). So please read this question twice before marking ...
8
votes
1answer
356 views

Tile-laying for beginners

Coldport is celebrating having a new town hall by laying a tiled design in the public square in front of the building. The design is also square: $5\times 5$ tiles square, in fact, and features three ...
-1
votes
1answer
125 views

Find the lowest floor from which Venus eggs break [duplicate]

Venus gave you two eggs because she wants to test their strength. She lives in a 100 floor building and she wants to find the first floor above which the eggs break when thrown out of the window. ...
9
votes
3answers
385 views

A box full of unfair coins

Lolek and Bolek are arguing on whose turn is to take out the trash. They have a box with $n$ coins. when the coin $i$ is thrown, the probability that it lands on heads is $p_i$. They decided to make ...
3
votes
1answer
146 views

Mathmatical equation answer [closed]

I think there must be a way to solve this but I can't get there Green + Blue = Yellow Red + Green = Purple Yellow - Purple = Red Red + Green + Blue = 9 I have made some progress And but I run ...
-4
votes
1answer
267 views

How many eyes do we have? [closed]

If a giraffe has two eyes, a monkey has two eyes, and an elephant has two eyes, how many eyes do we have? The question is not guess work.. it has definite answer.
3
votes
1answer
124 views

Perambulating ants 2

The ants from this puzzle have been placed into a new arena: a cross-shaped hallway with a pillar (black square) in the centre and four statues (numbered 1-4) set symmetrically. The ants, like last ...
-1
votes
1answer
149 views

8-puzzle in 12 steps

This quiz is about the 8-puzzle. It is a board with 9 spaces. There are 8 tiles with the numbers 1 through 8. One space is empty (.). You slide the tiles around the ...
15
votes
9answers
4k views

Three people wearing hats

Ms. Doha gave hats with different non-zero single digits (two of which are factors of the third) to Ms. Haha, Ms. Lola and Mr. Hehe. The three of them can't see the digits on their own hat though they ...
11
votes
2answers
804 views

Perambulating ants

An ant is a methodical creature, and the ants in this puzzle are particularly so. When they start walking they always walk in a straight line, and when they reach a boundary they always turn exactly $...
3
votes
1answer
168 views

Stuck on (a couple of) diagramless kakuros

I was working through OAPC 6 (http://oapc.wpc2009.org/archive.php?id=46). I was having trouble with the diagramless kakuros. The rules for this puzzle are as follows: Place the numbers $1-n$ (7 and 9 ...
1
vote
3answers
190 views

Blood Type Puzzle 2: Am I Pure Blood?

This puzzle is similar to the first puzzle but with a few twists: In this question: both my mom and I are blood type B. But this time I don't know my dad's blood type. My mom said her parents ...
3
votes
8answers
489 views

Two doors, two guards, and two keys

Table of contents Introduction - read about where the puzzle comes from. The puzzle - read the puzzle itself. Warming up - read about solutions to a simpler variation of the puzzle. Introduction (...
4
votes
1answer
231 views

Ask, and you shall receive

Request of me twenty, receive of me twenty. Request of me sixty, your behest will be fulfilled. Request of me eighty, you'll be given the same; but ask for one hundred, and you will get only sixty. ...
12
votes
2answers
780 views

Hearts and Spades in a Row

From a deck of playing cards remove hearts ace to seven, and spades ace to seven. Now place them on a table in a row so that the number of cards between the two aces is 1, the number of cards ...
8
votes
2answers
311 views

Another coin weighing puzzle. But this is simple!

There are many coin weighing puzzles. So a general attribution to all of them. (And I will fully understand if you completely ignore this one). Hope this is not a duplicate. But I think this is a ...
7
votes
1answer
732 views

Queens full of jacks

(Note: I doubt that this puzzle is complex enough to post it here, but I still took a try.) There are 3 queens and 2 jacks (a full-house combination from poker) taken from a deck with standard suits, ...
2
votes
0answers
35 views

Using a balanced scale find the minimum and maximum weight of items [duplicate]

There are 1567 items with different weights. The goal is to find the item that has the maximum weight out of the 1567 and the item that has the minimum weight out of the 1567. For this you are allowed ...
7
votes
2answers
221 views

Turning a fan on

I bought an air purifier which has [off, low, medium, high] settings and a single button. If it is on, the first button press activates the lights and subsequent presses increment the level with off ...
-2
votes
1answer
160 views

Missing Number Picture Puzzle

This is is logical reasoning puzzle in which your challenge is to find the relationship among the given numbers and then find the value of the missing number. Source: https://www.funwithpuzzles.com/...
9
votes
5answers
498 views

2 fake coins from a pile of 30 coins

You need to find two fake coins from a pile of 30 coins. You know that a fake coin has a different weight to a real coin, but you don't know whether it is lighter or heavier. You also know that all ...