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
672 views

Seven treasure chests

Seven treasure chests, made of gold, silver, tin, steel, brass, pewter and lead, each contain coins of one of the seven metals. No two chests contain the same type of coin. The pewter chest does not ...
2
votes
1answer
457 views

Find the odd coin

You have 11 visually identical coins. One of them is marked genuine (and you know which one this is). Out of the remaining 10 coins, all but one of them are also genuine, but you don't know which ones....
21
votes
3answers
3k views

Ten Tricky Mathematicians

Somewhere on the Hyperbolic Plane, you encounter ten mathematicians. You know that some of them always tell the truth while the rest always lie. Each of them knows which of the others tell the truth ...
72
votes
13answers
15k views

Three logicians walk out of the bar

It is known that when logicians get drunk they may claim not to know the answer to a question when they should know it very well. After a night of heavy drinking at the bar, three logicians decide ...
5
votes
1answer
573 views

The Minotaur's Labyrinth

You are trapped in a chamber in the center of the Minotaur's Labyrinth. There are $\mathbf{N}$ tunnels, $\mathbf{m}$ of which lead to safety; the remaining tunnels only lead back to the chamber. Each ...
7
votes
1answer
252 views

Guess another's present 2: Generalised

What if in Guess another's present problem introduce more present's colours? Also i would reduce a number of men to number of colours. So the task basically the following: N clever men receive ...
7
votes
6answers
791 views

Guess another's present

100 clever men receive presents from the president. Each man gets either a red or blue present, and only knows the color of his own gift. Then each man must guess a colour of a gift of some man: he ...
-5
votes
1answer
313 views

What are the missing items of this number sequence? [closed]

1, 2, 5, 13, ?, ?, 1 Please give explanation.
-1
votes
1answer
14k views

Who is the murderer? - logic puzzle

Three men are arrested on charges of murder. They make the following statements. First suspect: I'm not guilty of murder. Second suspect: the third suspect is the murderer. Third suspect: the first ...
5
votes
4answers
1k views

Find the missing object

1. 2. 3. 4. 5. 6. ? 7. Find the missing object (No. 6) Note:The first one to post an object with the matching criteria will be the winner.
17
votes
2answers
3k views

Find the missing piece

One day I got a paper from my courtyard with the center portion missing. Here is what the poster looks like: I have made some pieces of paper so that I can stick one to the center of the poster. ...
-5
votes
2answers
317 views

Double the fun with two puzzles [closed]

Here are the two puzzles that I have heard a long ago from my friends. 1) You can touch it with your right hand, but not with your left hand. What is it? 2) 10x+4x = 2y Then, what is x and y? ...
8
votes
2answers
444 views

The Security To The party [Part 23]

A party is being held at a local mansion. The host is very rich and his success is because of one thing ~ his famous recipe for Spaghetti! The only guests that may attend are people the host knows ...
6
votes
1answer
363 views

Draw the item after decoding the instructions

Draw the missing item replacing the question mark
7
votes
1answer
415 views

Chess tournament problem

12 chess players took part in a tournament. Each played against each other exactly once. After the tournament every chess player did 12 lists of names. On the first list, the player only wrote his ...
8
votes
2answers
2k views

Is it Always Possible? Colour Flipping

There's a 4x4 square, where switches are either red or green. When you flip a switch, all the buttons on that row and column will change color. Is every starting position possible to complete? If not ...
4
votes
1answer
336 views

Who are the guilty parties? #3

You've barely got back from the isolated villa where your last case was, when you hear that you are needed again: There is a group of people on board a yacht. The wealthy owner and her spouse have ...
-3
votes
2answers
483 views

Guess the missing alphabet!

What is the missing alphabet in below sequence? M T W T _ _ S
-2
votes
2answers
235 views

What cannot stand outside a door? [closed]

Let there be a house of which there is a beautified front door that is closed. Now: what is that "thing" for which it is impossible, logically (and irrefutably), to be outside this closed door?
20
votes
8answers
11k views

Logic puzzle - 3 suspects

An inspector knows that exactly one of 3 suspects committed a crime, and interviews them to find out which. Each person lies one time, and tells the truth the other time. A says: I did not do it. B ...
5
votes
1answer
371 views

Who Are The Guilty Parties? #2

You've barely got back from the island where your last case was, when you hear that you are needed again: There is a group of people at an isolated villa. In a curious twist, the aristocrats have ...
2
votes
1answer
557 views

Who are the guilty parties? #1

(Your investigations continue here.) I am testing this puzzle to see how it works, and gauge the difficulty. I have plans which will be unveiled in future puzzles of a similar nature, pending ...
20
votes
3answers
1k views

The mysterious card in the middle

The referee tells Lefty, Righty, and Middly: "I have picked three positive integers $L,M,R$ with $L<M<R$ and $L+M+R=13$, and I have written these numbers onto the three cards lying face down on ...
7
votes
1answer
688 views

The Beautiful Ladies' Brothers

The ladies mentioned in Five beautiful ladies have five brothers: Adam, Bob, Charlie, David, and Edward. Three have hazel eyes and are honest; two have lime-colored eyes and always lie. You are ...
1
vote
2answers
309 views

Simplest Magic Fruit Split with Magic Number [duplicate]

Anyone who plans to visit the Miracle Fruit Tree in the Royal Garden has to travel through Seven Gates in each of the Seven Curtain Walls surrounding the garden. Each of these gates has a guard. ...
-2
votes
1answer
3k views

Bus Driver's Age? [duplicate]

Imagine: You are a bus driver that drives from Delhi to Karachi and exactly 1987 kilometers. 1 liter fuel can end upto 105 kilometers . Every time driver stops at a fuel station he fills 3 liters of ...
1
vote
1answer
663 views

Find the missing value

find the value of 1 + 7 from the following. 3 + 3 = 3 5 + 4 = 4 1 + 0 = 3 2 + 3 = 4 3 + 4 = 5 1 + 7 = ?
0
votes
6answers
9k views

Missing number in a circle? [closed]

Here in this circle there are seven segments. 6 numbers have been written in 6 segments following a particular pattern. Find the number which will replace ??? in the seventh segment and also describe ...
7
votes
5answers
522 views

Ahmad, Ali, Amir and Nima in a tournament

Four players with first names Ahmad, Ali, Amir and Nima participated in a tournament. The highest ranked player defeated the other three, the second ranked player defeated the players in rank three ...
3
votes
2answers
6k views

Find the direction of the disc

You have a disc. One half of the disc is painted white and the other half is black. The disc rotates in either a clockwise direction or an anti-clockwise direction. There are two sensors which are ...
8
votes
10answers
3k views

A tiny question: The little big family

In a family, there are the following human members: Grandfather, grandmother, father, mother, son, daughter. All family members are inside a single room now. Question: What is the minimum amount of ...
5
votes
3answers
2k views

Crossword Puzzles: What is this crossword type?

I found these rules for a crossword, but I don't know what type it is. Can anyone help me? The rules: The words are given and you're asked to place them on the grid! The grid and the list of ...
11
votes
3answers
2k views

Creating a solved 9x9 Sudoku based on certain rules

The question: A rectangular fence is a set of 4 cells on a solved sudoku grid with co-ordinates $(i,j)$, $(m,j)$, $(m,n)$ and $(i,n)$. You can visualize this as the 4 corners of a rectangle. ...
12
votes
4answers
7k views

Who is the thief? An elementary school teacher had her purse stolen

Its not mine. I found it and didnt find it when i searched so i hope you guys enjoy. I did edit it somewhat. An elementary school teacher had her purse stolen. The thief had to be Sammy, Karin, ...
18
votes
6answers
4k views

Guess five binary digits!

Person A thinks of a 5 digit binary number. Person B tries to guess the number. B can guess a 5 digit binary number and A will respond with the number of correct digits (digits in the right place). ...
2
votes
2answers
320 views

Closing taps (generalisation) [closed]

You have a tanker that can hold any amount of water. You have $n$ taps that either let in or let out water. The rate of flow of water (in $ml/min$) for each tap is given by $f_n$ (positive for inflow, ...
5
votes
2answers
755 views

I Was Told It Would Explode

Story: There is a line of bombs, all over a building. You are the bomb defusal expert, and you are the one everyone is counting on the save the city, for as if any one of the bombs go off, you, and ...
-2
votes
2answers
256 views

Colored stones on a chess board puzzle [closed]

We have a chess board of size n x n and there is exactly one stone on every square. We have green, blue and red stones. We must not have a row or a column full of stones of the same colour. We can ...
6
votes
3answers
2k views

Another village of liars and truth-tellers

There are two kinds of people living in a village: those who always lie (liars) and those who always tell the truth (truth-tellers). Everybody knows each other in the village and therefore knows ...
10
votes
2answers
890 views

The final showdown

I am amazed at my adviser's brilliance once again. Blackbeard's vanguard fleet was quickly sunk. And as luck would have it, the moment we finished cleaning up the mess, the scout returned with the ...
-1
votes
2answers
271 views

The Hallway and Tele Doors ~ Prolong the Inevitable

Sequel to: The Hallway and Tele Doors Note: You need not have to read the above to understand this puzzle, however this puzzle does spoil the above one. The tele door system: Each pair of doors, ...
7
votes
1answer
723 views

mistakes in analogous puzzles from The Tipping Point

In the book 'The Tipping Point', Malcolm Gladwell cites two puzzles and draws an analogy between them, in fact he claims the two are equivalent. I believe there are some problems with both puzzles, ...
8
votes
1answer
402 views

End of piracy and beginning of technology

Blackbeard is no more, and everything seemed peaceful again, but during the last engagement with Blackbeard, my military adviser got introduced to the concept of "computer", and became very interested ...
5
votes
2answers
623 views

Find multiple dishonest people

Recently I travelled far distance by train and a stranger told me this riddle but I never got the answer: 100 years ago, when far distance travelling was something special, a traveller came back from ...
7
votes
1answer
485 views

Prepare for the counterattack

My adviser's brilliance crushed the Blackbeard's fleet, and we held a banquet to celebrate. The banquet was short lived however, for a arrow flew right past me and struck a pillar. Attached was a ...
8
votes
1answer
586 views

Dinosaurs and Elephants

There are two species living in the land of Puzzling: elephants and dinosaurs. Elephants always tell the truth when talking about an elephant, but always lie when talking about a dinosaur. ...
15
votes
2answers
1k views

Help with the name of this puzzle

When I was cleaning my basement I found one puzzle that my father gave me when I was a child. I really want to know the name of it! Could someone help me? The puzzle consist in 4 disks, and each ...
12
votes
2answers
648 views

Help locate enemy fleet

Few days ago, the notorious Blackbeard sunk 3 of my ships carrying exotic goods and treasures from Asia. I was furious and I am determined to send out my fleet to bring him to justice. However, as he ...
13
votes
6answers
1k views

The Hallway and Tele Doors

Assume you have an unlimited but finite number of linking, teleporting doors you can add to a hallway of finite length. Assuming there's a door at the start and finish, can you arrange the teleports ...
1
vote
3answers
1k views

Where are the missing guests?

I'm Caucasian and my fiancé is Chinese - I met her on a trip to Tahiti though as chance would have it, it turned out that we actually grew up in adjacent towns in Ohio. We decided to have a very ...

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