# 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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22answers
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### In the 100 blue eyes problem - why is the oracle necessary?

The riddle Randall Munroe (of xkcd fame) has, a bit hidden on his site, a logic puzzle: A group of people with assorted eye colors live on an island. They are all perfect logicians -- if a ...
13answers
21k views

### This is it. This is the one. Find your wife

If you have found her, maybe you could try saving her? You come home one day and find your wife is out. You open your computer and discover an email from her. To xxxxx, / Curiosity killed the ...
7answers
43k views

### Mensa IQ test question made by www.bergmandata.com

Which of the 8 tiles below is missing? I've been trying to figure out the answer to this question for quite some time. Can anyone spot the pattern?
15answers
38k views

### My wife has died

In 1980, a man lives on the 30th floor of his building. Every morning he wakes up, gets ready, kisses his wife, takes the elevator down to the first floor, and goes to work. One morning, he wakes ...
16answers
1.0m 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 ...
9answers
16k views

### Five coloured doors, which leads to freedom?

You have been incarcerated in a high-security prison for several nefarious crimes which we need not go into here. The warden, being a kindly logician, offers you a single chance to escape. You are ...
2answers
40k views

### 3 Logicians Walk Into a Bar

Three logicians walk into a bar. The barman says, 'Does everybody want a drink?' The first logician says, 'I don't know.' The second logician says, 'I don't know.' What does the third logician say? ...
7answers
16k views

### Thanks, dad! Never again

No idea why my dad dragged me into this place. Some guy is performing on the stage. He's reading numbers out loud. I think it's some kind of a sequence puzzle. 1... 8... 9... 16... 17... ...
18answers
15k views

### Nine gangsters and a gold bar

One night nine gangsters stole a gold bar. When the time came for dividing the bar, they faced a problem: two of the criminals put guns to each other's faces. Now it's up to fate whether one of them ...
11answers
22k views

### Correct way to add 22 to 4 to get 82

Inspired by this other puzzle, tell me a correct way by which adding 22 to 4 will give 82. As in that other puzzle, these numbers are all expressed in base 10.
9answers
13k views

### Is a married person looking at an unmarried person?

I remember answering this one incorrectly and when the answer was explained to me I was annoyed with myself. Here is your chance, with the original word phrasing: Jack is looking at Anne, but Anne ...
2answers
6k views

3answers
5k 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 ...
6answers
31k views

### Hats and Aliens

Here's a neat little puzzle taken from a Google interview question: 10 humans are abducted by aliens; each represents 10% of the entire human population. The aliens give each abductee either a ...
2answers
4k views

### Reverse Puzzling

George is a great puzzler, so I was extremely surprised when he didn't immediately know the answer to a really famous puzzle. It's a puzzle that you probably did years ago, and have heard so often ...
1answer
2k views

### The Persistence Of Memory

You find yourself on the floor, slowly waking up and unable to remember how you got here. As you slowly come to your senses, you realize that another weird guy has trapped you in another unfamiliar ...
8answers
31k views

### How did the police know?

One night, a man receives a call from the police. The police tell the man that his wife was robbed, murdered, and her body dumped in a remote location, and that he should reach the crime scene as soon ...
5answers
6k views

### Burning ropes as timers

You have 2 identical ropes which burn at a specific rate, and an unlimited supply of matches. When you light one end of a rope, the fire will take exactly 1 hour to travel to the other end of the rope....
5answers
5k views

### Who poisoned Hugh G. Pokitz? (a murder mystery logic puzzle)

Preface After your last mishap with a heap full of rabbits, you got sick of being lied to. Isn't life just so much easier when you can conclusively tell if someone's been telling the truth or not? ...
7answers
5k views

### Amnesiac in a ring shaped palace

Related: Turn off all lights in a ring-shaped palace Your boss has trapped you inside a ring-shaped palace, and all you know about the palace is that there are some number* of identical rooms, each ...
9answers
5k views

### An old picture puzzle

Here is a drawing of an old picture. Your task is to answer all 8 questions correctly AND give a good reasoning for it What time of day is it? Is it early spring or a late fall(autumn)? Is this river ...
7answers
9k views

### Guessing hat colors. 4 prisoners

This is a variant about guessing hat colors. You may want to try Hats and alien or Guessing hat colors or Four prisoners wearing black and white hats. Statement 4 prisoners are to be executed. ...

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