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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).

87
votes
15answers
851k 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 ...
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. ...
46
votes
10answers
15k views

Puzzle: Who hacked the computer?

I was working my way through some Knight and Knave Puzzles in Discrete Maths by Rosen, when I came across the following question: Four friends have been identified as suspects for an unauthorized ...
42
votes
11answers
8k views

3 doors, three guards, one stone

You are in a room with three doors. You find out that behind two of these doors, the darkest pit of hell is waiting for you to make a mistake. The other door leads to heaven, where you obviously want ...
38
votes
3answers
11k views

How many liars are in the room?

There are five people in a room. Each person is either a knight, who always tells the truth, or a liar, who always lies. Each person is asked the following question: How many liars are among you?...
35
votes
12answers
9k views

Batman vs 4 villains

One day after having his morning Bat-coffee, Batman received the following message on his Bat-computer: Hello there Dark Knight. I, the Riddler, along with Joker, Two-Face, and Penguin, are ...
35
votes
8answers
6k views

Who committed the crime?

A crime has been carried out by one person, there are 5 suspects. Each suspect is asked under polygraph who they think committed the crime. Their answers are as follows: Terry : It wasn't Carl, It ...
34
votes
16answers
5k 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 ...
33
votes
23answers
5k views

Unfortunately, you died [closed]

Your soul is on its way to the afterlife when suddenly you arrive in a room. You look around and notice six humanoids staring at you. You walk toward them and you can suddenly hear them talk between ...
33
votes
10answers
6k views

Liar liar pants on fire

Here is an easy and straightforward liar puzzle. Four people are in a room, stack reader, boboquack, Rand al'Thor and Brent Hackers. stack reader states that at least 2 of the other 3 are liars. ...
32
votes
9answers
9k views

Which offer is better?

You are to make a statement. Of these two offers you have to choose one; which one is more profitable to you, and why? If the statement is true, you get exactly 10 dollars. If the statement is false,...
31
votes
12answers
6k views

Knights, Knaves and Normals

In the kingdom of Boolistan, every inhabitant is either a Knight, Knave or Normal. Knights can only make true statements, Knaves can only lie, and Normals must either tell the truth or lie. Warmup: ...
28
votes
13answers
90k views

Three Doors, One Truth-Teller, One Question

You are in a prison. There are 3 doors, and a ghost standing in the middle of the prison. He says one of the doors is the way to freedom while the other two lead to death. You get to ask only one ...
28
votes
7answers
10k views

Who killed Jeremy?

Jeremy was killed. Peter claims that Tom is guilty. Tom says that Ralph is guilty. John swears he didn't kill Jeremy. Ralph says that Tom is lying. If only one person is telling the ...
28
votes
1answer
3k views

Murdered down the Rabbit Hole (a long logic puzzle)

Backstory Disaster has struck for Leporidae throughout the fantasy realm -- a mass carrot famine has wreaked havoc upon all existences but our own. Because of this, 25 of the leading fantasy bunnies, ...
27
votes
5answers
1k views

Council of Magic - a palace of deceptive spellcasters

Council of Magic: The King of Puzzlington has sent you to a distant palace to gain the aid of the Council of Magic. As your luck would have it though, spellcasters are a tricky sort. There are 4 ...
26
votes
6answers
5k views

Out of these 20 Doors, Which One Leads You to the Jackpot?

Congratulations for achieving this final stage of "Millionaire Super Logic" show! Once again, my name is Athin, and I'll be your host to help you win the jackpot of one, milLION, DOLLARS! *audience ...
26
votes
5answers
5k views

You trolls, get out of my party!

You have invited $2017$ of your acquaintances to a party. But after they all arrive, you come to know from a reliable source that each of your guests is either a troll or a true friend. You don't know ...
25
votes
11answers
5k views

Kill the jokers! - Part 1

The famous and ruthless explorer Wyoming Wilbert reports in one of his books that he once visited an island inhabited by jokers and truth tellers. Truth tellers always tell the truth, whereas jokers ...
25
votes
10answers
4k views

Liar and the Truth teller with 6 inhabitants

There are two types of people on an island: truth tellers and liars. Truth tellers always tell the truth, while liars always lie. A foreigner meets six of the inhabitants, and asks each of them the ...
25
votes
4answers
7k views

King Octopus and Servants Puzzle

Puzzle: King Octopus has servants with six, seven, or eight legs. The servants with seven legs always lie, but the servants with either six or eight legs always say the truth. One day, 4 servants ...
23
votes
3answers
2k views

A Space Station 13 tricky situation

You are the Captain of the Space Station 13, and everything went bad very quickly. Most of the crew died, and it took you not so long to figure out that some people are not who they're supposed to be (...
22
votes
6answers
10k views

Which teacher is the murderer?

In the first day of a new class semester, a student was murdered inside the classroom. No witnesses, no murder weapon, and no evidence. The police got four teachers as possible suspects, but they all ...
22
votes
2answers
5k views

The village of the liars and truth-tellers

I read this puzzle in an Italian newspaper some days ago. It reported it was asked at one of the latest Mathematical Olympiads. It's not difficult, but it requires some logical thinking. I'm posting ...
22
votes
4answers
1k views

Art Accident at Airport!

There was an accident at the airport! A hanging art installation fell and landed on some passengers. In addition to tearing up all their tickets and mixing up their luggage, six people sustained ...
22
votes
3answers
2k views

The last question to the guards

"What will happen next?" asked the old man. His voice was friendly, his eyes bright, as always. His hair and beard seemed to be even whiter than ever before. "The standard procedure is as follows: ...
21
votes
6answers
4k views

The Knight never lies, the knave always lies, and the spy either lies or tells the truth

A says he is not the knight, B says he is not a spy, and C says he is not the knave. Who is who?
21
votes
5answers
3k views

Knights and Knaves : Liar , Liar - How many are you?

There are 2014 persons in a row Each of them is either a Knave (who always lies) or a Knight (who always tells the truth). Each person says 'There are more knaves to my left than knights to my ...
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 ...
20
votes
8answers
9k 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 ...
20
votes
5answers
2k views

Knights and knaves in Landilandia

You're traveling on a hiking trip in the land of Landilandia when you encounter a forest. The notes in your guidebook tell you that there's a safe route here leading into the woods, but when you ...
19
votes
4answers
6k views

Who stole the flying car in Hogwarts?

During a trial in a Hogwarts court, Ron claimed that the Flying Ford Anglia car was stolen by Hermione. Then Hermione and Harry gave testimonies which, for some reason, were not recorded. Later on ...
18
votes
4answers
2k views

On which day The Joker usually going on a date?

You are an investigator. You are to investigate The Joker to know on which day he usually goes on a date with Harley Quinn. The Inspector said that The Joker is lying if and only if it's Monday, ...
18
votes
5answers
3k views

Statements that the deities True and False cannot say

You over exert yourself working on logic puzzles and die of exhaustion. You are awoken by the omniscient deities True and False. True only speaks true statements and False only speaks false statements....
18
votes
3answers
1k views

Edward and the seven imps' Game

Excerpt of “Manipulating the Fabric of Space” “Miscasting translocation spells can have many nasty consequences. The caster’s body could be warped or torn apart, his soul could be separated ...
18
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 ...
18
votes
4answers
2k views

Past, Present and Future

There are 3 gods, named Past, Present and Future, who all look identical. They sit in a throne room, with one in the middle, the others on the right and left. You are allowed to ask them a series of ...
17
votes
6answers
6k views

A death at a restaurant

You are a mafia leader and because of mysterious recent developments, you had to call the meeting of heads which is happening right now at your's cousin restaurant. The problem is, after the opening ...
17
votes
4answers
2k views

Can anything be deduced from the statement “If I am a truth teller, the other two are liars”?

There is a scenario which goes along the following lines: There are three friends. The friends are either truth tellers, or liars. One friend makes the statement: "If I am a truth teller, the ...
17
votes
3answers
3k views

Knights and jokers

There are $N$ men. $K$ of them are knights, $M$ of them are jokers. $N$ is known, $K$ and $M$ are unknown. You know that: $K + M = N$, $K \gt M$, $M \ge 1$, $N$ is odd. Knights always tell ...
17
votes
1answer
2k views

The Pirates of Beal Isle - very long logic grid puzzle

Story Let me tell ye a tale: Somewhere northeast o' the Bahamas there be a tiny scrap o' rocks stickin' up out o' the sea known as Beal Island. It be a barren, rocky place, and no man ever called it ...
16
votes
6answers
4k views

99 doors to death!

You wake up in a small locked room of a huge castle. There are 100 doors, numbers 1 to 100, and you are to open one of them. Open the correct door, and the entire castle is yours to keep. Open any of ...
16
votes
11answers
8k views

Knight, Knave and Joker puzzle

Here is an excellent puzzle with 3 types of characters: You are lost in a town and meet 3 men. You somehow (God told you) know that they are Knight, Knave and Joker. Knight always tells truth, ...
16
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, ...
16
votes
1answer
540 views

Find the number from 10 statements

You are given the following ten statements and are asked to determine a particular number. At least one of statements 7 and 8 is true. This either is the first true or the first false ...
16
votes
3answers
2k views

Lies, damned lies, and statistics

A (hopefully) new variant on the Knights & Knaves problem. On the island of D'Israel, the inhabitants fall into three types: Liars, Damned Liars, and Statisticians. They are visually ...
15
votes
5answers
3k views

Who led the mutiny?

You are were might still be a sea captain. On the 14th of December, 1214, your sailors rebelled. 6 sailors and your first mate get in a boat to row you to what they believe is an abandoned island. ...
15
votes
9answers
3k views

Find the correct door!

This is my first puzzle but I hope it will work out well and that everyone can enjoy it. While trying to get out of a dungeon, you arrive in a circular room with 5 doors at equal distances from each ...
15
votes
2answers
993 views

Town of liars and truth-tellers with eccentric mayor

There is a small town with a strange custom. Residents each own a single pebble, painted blue or red, which they always carry in their pockets. Those with blue pebbles always tell the truth, and those ...
15
votes
2answers
1k views

Automatically a Knight, Knave, and Joker

Let M be a finite positive integer. It's exact value is not known. Suppose we have three classes of automaton, all of which accept a bit stream as input, produce a bit stream as output (one bit per ...