Questions tagged [liars]

Puzzles that focus on getting information from truth-tellers (who never lie), liars (who always lie), and Jokers (who answer at random).

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6
votes
1answer
229 views

Smullyan Logic Puzzle about Nelson Goodman Principle - Knights and Knaves

In Smullyan's "Logical Labyrinths" there is the following problem 1.11: ...
8
votes
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 (...
2
votes
1answer
268 views

What is the smallest number of lies needed to solve a Dragon Joust puzzle?

I recently watched this video which presents a deduction "riddle" about dragon jousting. The rules for the puzzle (from the video) are as follows: After centuries of war, the world’s kingdoms have ...
4
votes
2answers
2k views

Alternate answer to the 2 guard 2 door question?

I asked a friend the classic question about the two guards and two doors that goes as follows: The rules are clear: there are two doors. One leads to the castle, the other, to certain death. You may ...
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, ...
38
votes
17answers
6k views

XKCD inspired logic puzzle

I came up with a logic puzzle inspired by this xkcd comic. I don't yet have an answer, and I am wondering if anyone can come up with one. You are in a room with three doors. Two of the doors lead ...
3
votes
8answers
506 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 (...
10
votes
9answers
11k views

Survive from death by asking the right question from trolls

You are in the intersection of two roads, there is a troll in the beginning of each road. One of them is liar (always lies), and one of them always tells the truth. One of the roads, ends to your ...
7
votes
1answer
1k views

A fish story on aymara language

Interesting story I stumbled upon: Aymara is a South American language spoken by more than 2 million people in the area around Lake Titicaca. Among the speakers of Aymara are the Uros, a fishing ...
7
votes
1answer
251 views

The scales never lie (oh yes they do!)

There are $10$ coins, one of which is a fake, and weighs either more or less than the others - you don't know which. There are two sets of scales - one tells the truth, the other lies (always says ...
6
votes
4answers
866 views

Knights and Knaves in the Wild West

Late at night at a bar in the Wild West only two cowboys from out of town are left, playing poker with the barkeeper. One of them cheats, so another throws over the table and they have a fistfight (...
43
votes
11answers
8k views

3 doors, three guards, one stone

You are in a room with three doors. Behind two of them, the darkest pit of hell waits for you to make a mistake. The other door leads to heaven and freedom. Each door is guarded by a guard: Michael, ...
13
votes
8answers
4k views

2 Guards, 3 Keys, 2 Locks

There are 2 guards: one only tells the truth, the other only lies. There are 2 locks and 3 keys: each lock can only have 1 key matched - the 3rd key doesn't do anything. You can only ask one ...
7
votes
4answers
430 views

Island of Knights, Knaves, Spies

There are 3 types of inhabitants of a village: knight, knaves, normal. You should map each inhabitant with its type, by asking only this type of question to a person: "Hey X, what is the type of ...
4
votes
2answers
230 views

Knights and knaves puzzler

A very special island is inhabited only by knights and knaves. Knights always tell the truth, and knaves always lie. You meet three inhabitants: Peggy, Joe and Zippy. Peggy claims, "I am a knight or ...
3
votes
2answers
115 views

Knight and knaves

A very special island is inhabited only by knights and knaves. Knights always tell the truth, and knaves always lie. You meet three inhabitants: Alice, Rex and Bob, where Alice tells you that "Rex is ...
6
votes
18answers
4k views

Ask one verbal question to figure out who is blind and who is mute among three persons

This is another "You can ask only one question" puzzle. This is an edited very restricted version There may be multiple answers but I could come up with only one. There are three persons in three ...
36
votes
10answers
5k views

Knights and Knaves: What does C say?

You are on a fictional island with two types of people: knights who always tell the truth, and knaves, who always lie. Three of the inhabitants - A, B, and C are standing in the garden. A says, "B and ...
97
votes
16answers
984k views

Two doors with two guards - one lies, one tells the truth

You are a prisoner in a room with 2 doors and 2 guards. One of the doors will guide you to freedom and behind the other is a hangman --you don't know which is which. One of the guards always tells ...
1
vote
0answers
60 views

Survive from death by asking the right question twist [duplicate]

You are at a path and there is two roads splitting from it. The first one is certain death and the other is the way home. You do not know which way is the right way home, but there are two people. ...
6
votes
4answers
578 views

Simple logic puzzle

We think of an island inhabited by rogues and knights. Rogues are always lying, knights always speak the truth. One day 12 islanders come together among which is at least one knight and at ...
8
votes
12answers
3k views

Time to call the bluff [closed]

You are located outside of two rooms which have a door between them. Each room has one or more computers whose total power is unknown, so they cannot be reliably used as proof-of-work to compare times,...
8
votes
2answers
264 views

Knights and Knaves on a (Not So) Deserted Island

One day, while flying your single-engine seaplane out over the Pacific, the electrical system shorts out, all of your electrical systems (including the radio) fail, and the engine dies. You are in a ...
12
votes
4answers
4k views

The joke office

Alice and Bob are supposed to get form A at the joke office. Forms A, B, C, D and E are each at exactly one of the following five terminals. At one Terminal is only one form. Terminal 1: Here ...
2
votes
1answer
232 views

The chariot race

In a chariot race only 4 cars came to the finish: the blue, the green, the red and the white one. Titus, who is in bed with a cold, inquires to Quintus about the outcome of the race, because he ...
21
votes
8answers
3k views

Robots in a spaceship

Xerxes has 6, 7 and 8-arm robots in his spaceship. Unfortunately, the 7-arm robots are misprogrammed and everything they say is a lie. The other robots are fine, they always speak the truth. Once ...
14
votes
2answers
749 views

The alcoholic village festival

The villages Arriba and Abajo together have 2019 inhabitants. At the annual festival are more than 2000 villagers this year. When they form a huge circle for dancing, everyone calls happy: ...
15
votes
3answers
2k views

The warming up game

The theater group began today with a warming up game. Everyone has been assigned a role and is now either a bad guy who always lies, or a good guy who always tells the truth. Max, who comes late, ...
1
vote
2answers
421 views

T Knights, L Knaves and R Jokers

Following these questions: Faulty computers, Knights and jokers I wonder, what if the conditions are the following: We have T Knights (truth-tellers), L Knaves (liars) and R Jokers (random-...
9
votes
2answers
655 views

Six liars, truth-tellers and jokers

As in this puzzle, there are three different kinds of people: truth-tellers (always telling the truth), liars (always lying) and jokers (who may either tell the truth or lie). Based on these aspects ...
12
votes
5answers
1k views

Meta Knights and Knaves Puzzle with Hats

I landed on the island of Knights and Knaves where Knights always tell the truth and Knaves always lie. I set out to find their two leaders, Raymond and Martin and I really wanted to talk with Martin....
6
votes
2answers
295 views

Liars, truth-tellers and jokers

In a strange village there are three kinds of persons: knights (always telling the truth), knaves (always lying) and jokers (who may either tell the truth or lie). A, B, C and D live in this village, ...
4
votes
1answer
258 views

Four Doors, One Escape

You are trapped in a room with four adjacent doors upon a wall. On each door is one of the first letters of the alphabet, in order, from left to right. You know that one of the doors leads to freedom, ...
7
votes
3answers
630 views

Three knights or knaves, three different hair colors

In a group of three people (A, B and C), everyone has a different hair color (blond, black or brown, not necessarily in this order) and everyone may be either a knight (always telling the truth) or a ...
4
votes
1answer
380 views

Lying under arrest

I'm in a custody, under arrest, no contact with the outside world. I do not know if in that jurisdiction authorities are allowed to lie. Some real-world knowledge suggest lying by authorities is ...
3
votes
2answers
150 views

The truth within

Someone living in the remote cabin that you do put a virus onto your PC. Here are your suspects: Your brother, Liam, who only tells the truth about his opinions. Your sister, Irene, who tells the ...
19
votes
5answers
1k views

Island of Knights, Knaves and Spies

There is an island with $N$ inhabitants (for example $A_1, A_2, \dots, A_N$), each of them is either a knight, a knave, or a spy. As usual: knights will always tell the truth upon answering a ...
3
votes
5answers
385 views

A story about liars

Evelyn, Skylar, Alayna, Madelyn, Jonathon, Lara, Alyin, Felix, Iris, Bob and Roslina live on an island where some people always tell the truth, and the rest always lie. Roslina says "Alyin and Evelyn ...
10
votes
1answer
1k views

Island of Liars

A king goes to an island, where there are 5823 people who always tell the truth and 8723 who always lie. The king is special guest for the party celebrating 2053 year. On the party, liars and ...
48
votes
15answers
6k views

Find the identity of the four troll brothers

The four troll brothers Wudhor, Xhaqan, Yijlob and Zrowag have the following properties: Wudhor always says the truth. Xhaqan always lies. Yijlob lies or says the truth unpredictably. ...
10
votes
3answers
13k views

Knights , Knaves and Spies - Part 1

I was working my way through some Knight and Knave Puzzles in Discrete Maths by Rosen, when I came across the following question: There are inhabitants of an island on which there are three kinds ...
1
vote
2answers
357 views

Brain twister. A simple riddle to play [duplicate]

You are lost big crowded (monster). There are only two human living Jacobe and Recode . Your task is to reach your home, there are two routes and you are confused. Conditions: Jacobe always tell the ...
2
votes
2answers
82 views

Does it exist a way to solve visually by using a grid or to find the truth among a set of five people telling different statements?

I am having problems with trying to solve this riddle therefore I am looking for help. The situation is as follows: At a semiconductor laboratory in Hsinchu a security guard caught five ...
5
votes
6answers
698 views

You meet Yessayer, Nosayer, Truther, Liar

You meet 4 persons you haven't seen before, and must ask questions to determine who is who.They know each other, and their friends' behaviour. You may ask each as many times as you want but only yes/...
-1
votes
2answers
113 views

who eats more fruits? [closed]

in a party 3 brothers discussing: first brother says " I ate more fruit than 2nd brother and 2nd brother ate more fruit than 3rd brother" 2nd brother says " 3nd brother ate more than me also 3rd ...
6
votes
3answers
566 views

Monty's Labyrinth

(A fun combination of two classic puzzles, hope seasoned puzzlers enjoy.) Having escaped through almost all of a labyrinth, you are met by three magical doors. Two of them lead to certain and ...
6
votes
1answer
1k views

Classic two guards and two doors

I recently heard a version of the classic two guards (one is a knight who always tells the truth and the other is a knave who always lies) standing by two doors (one leads to certain death and the ...
3
votes
4answers
613 views

The Three Mystery People- An Actual Mystery

I believe almost everyone has heard this riddle before. There are three people in front of you. One always tells the truth, one always lies, and one answers randomly between truth and lies. You ...
4
votes
2answers
707 views

yes/no logic problem

There is a truth teller (always tells the truth), a liar (always lies), and one that sometimes answers truthfully and sometimes lies. Each person knows who is who. You may ask three yes or no ...
10
votes
1answer
734 views

Murder in the Royal Court

An entry in Fortnightly Topic Challenge #40: Retrograde Analysis! I can't believe it! Last night we heard a bit of fighting... but we had no idea that... our King was in check, and my fellow Rook and ...

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