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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8
votes
1answer
308 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
180 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 ...
7
votes
2answers
459 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)
18
votes
4answers
2k views

Four buttons on a table

I was asked lately (in an interview) to solve this puzzle, which is similar to the 4 cups on table puzzle. In a certain room there is a rotating round table, with 4 symmetrically located ...
11
votes
2answers
485 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
258 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 ...
-4
votes
0answers
108 views

What is the correct option here? [closed]

What is the correct option here? I believe it is like a to e? The question is from BUNQ reasoning test.
2
votes
4answers
214 views

Which figure is not needed in the pattern?

I have been trying to figure it out, but no logic so far. This question was given to me by the University of Sofia.
7
votes
1answer
252 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) ...
3
votes
2answers
104 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 ...
1
vote
1answer
220 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 ...
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 ...
0
votes
0answers
182 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, ...
11
votes
1answer
399 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 ...
11
votes
4answers
3k views

Guessing hat colors

Red or Black There are 3 children sitting on three chairs. The children can only look forward and all wear one hat. The hats are either black or red. They are a total of 5 hats, 3 are colored red and ...
4
votes
3answers
222 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 ...
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 ...
5
votes
4answers
4k views

Men digging holes

Suppose 9 men take 9 hours to dig 9 holes in the ground. (a) How many hours would it take 3 men to dig 3 holes? (b) How many men would it take to dig 54 holes in 54 hours?
8
votes
1answer
257 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 $ABCD$ ...
7
votes
1answer
167 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
2k views

How to solve Rubik's Cube using mathematical formulas? [closed]

I am trying to solve Rubik's Cube, but it took one month for me when I started. Are there any mathematical formulas, rules and tips for solving Rubik's Cube in less time (i.e. minutes)?
36
votes
6answers
1k views

Sudoku embedded in a Kakuro

In addition to standard Kakuro rules, the grey shaded cells must form a valid Sudoku solution. One sum in this puzzle has been corrected from 28 to 23. Fortunately, it was in a location that nobody ...
-1
votes
1answer
149 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 ...
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
2answers
217 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
4answers
2k views

Measure the diagonal of a brick

You are given three identical bricks (cuboids) and a ruler (scale) as shown in the figure. You have to find the length of the brick's diagonal without using any formula and by using the ruler only ...
9
votes
1answer
402 views

Backwards Boggle

I came up with a fun little 1-player puzzle for myself to do when bored. Pick 5-6 words, preferably words that share a good number of letters, and try to create a Boggle board containing all of those ...
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,...
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 ...
10
votes
0answers
625 views

An enrypted clue for the police

A well known German drug dealer contacted his accomplice through an encrypted note. The police caught the accomplice during a drug deal and found the note in his backpack. Note: (For those who can't ...
1
vote
1answer
152 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, ...
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 ...
12
votes
4answers
26k views

Two doors with three guards - one lies, one tells the truth, and one is unreliable

This is an extension of Two doors with two guards - one lies, one tells the truth, but in this situation you are a prisoner in a room with 2 doors and 3 guards. One of the doors will guide you to ...
2
votes
1answer
307 views

What's that puzzle that goes like: Person A never lies, Person B always lies, etc?

What's the name of the puzzle where you're given something like: Person A never lies. Person B always lies. Person C I don't remember. Then it continues like: Person A says that person B is ...
19
votes
3answers
2k views

Star Puzzle: Determine which circles are True and which circles are False

A circle with number x means: “This circle is connected (straight line) to x circles with a true statement” This is valid only if the statement in the circle is True. If a circle is False, ...
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
75 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
168 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
264 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.
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 ...
8
votes
1answer
354 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. ...
3
votes
1answer
145 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 ...
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 ...
7
votes
3answers
891 views

Super Secret Cookbook

You requested the password for a super secret cookbook and received an SMS with the following content: 77733666688833 2555555 777772222337777 2663 777337555222233 84433 6688622337777777 9444844 ...
-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 ...
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 $...