# 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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### The Mysterious Disappearance of Doctor F. Andrews [Part 1]

This is my first real puzzle, so I hope you enjoy it! Sorry if the writing is a little poor, etc.. You are the unstoppable Detective Joshua Brown, and no puzzle can stand in your way! The Case: ...
4k views

### Is my sibling a sister [duplicate]

A male friend of yours wants to test if you are ok at Math and logical thinking, he says I am one of two children of my parents, and asks you to find out the probability that his sibling is a sister, ...
2k views

### The mad king and the 100 men who each have to guess the colour of their own hat [duplicate]

The following is the puzzle that I am trying to figure out. I know the "expected solution of 99". But honestly, I think this puzzle is flawed. How exactly can each wise man know the number of hats ...
608 views

### Left coin, Right coin, Last coin- A fair version

In this game, all players start sitting at a round table, each with a coin in their hand. At every turn, all players toss their coins together and put it on the table in front of them. Then each ...
450 views

Little Hans just got a model railroad kit from his grandfather for Christmas. His grandpa explained to him, that when he was young, he was a model railroad enthusiast, and encouraged his grandchild ...
585 views

### A Strange Sequence [duplicate]

This puzzle is taken from a French bestseller I read years ago. The solution is much simpler than it looks... Find the following line in this sequence : ...
552 views

### What's the sequence?

Joe likes 2025 but not 2024; he likes 529 but not 530; he likes 400 but not 500. Which does Joe like - 3600 or 3700? Why?
982 views

### A game of Green Jack

NB: This is based on a puzzle over at BrainBashers.com. The setup You and a friend play a card game called Green Jack. The deck consists of 16 cards, divided into 4 cards in 4 colors (standard ...
924 views

### Five professors and nine dishes

Here's yet another puzzle adapted from a puzzle book (in my case, with edits to make some of the specifications of the puzzle more clear because I didn't really understand them the first time I read ...
3k views

### Magic Squares in Sudoku Grids

A 3x3 magic square is a 3x3 grid containing the numbers 1-9 once each, and in which every row, column, and diagonal sums to 15: 294 753 618 And I presume we all ...
2k views

### The Illuminati and the Knights Templar

Some people in the American Senate are working for secret organizations. Some work for the Illuminati, some work for the Knights Templar, and some work for both. The are also innocent citizens who are ...
5k views

### Can you solve this logic puzzle in disguise? The color code behind the tomb

Another themed puzzle for you to enjoy. As with all my puzzles, please provided feedback about pro's and cons of the puzzle. The puzzle is self-contained (the link is just to provide a theme) and I ...
2k views

### Help me find my favourite DVD

I have an admission to make: I very rarely put my DVDs back in the case they came from. Whenever I watch a new DVD I just put whatever DVD is the player in the new case. I put the cases back on the ...
2k views

### Mutation of aliens

In the image you can see twelve mutation chambers (A to L). Each alien on the left side of the aliens goes through the three mutation chambers of its right side. The alien on the right side is the ...
3k views

### Come out alive from locked room [duplicate]

You are locked in a 50 x 50 x 50-foot room which sits on 100-foot stilts. There is an open window at the coner of the room, near the floor, with a strong hook cemented into the floor by the window. So ...
239 views

### The strange exchange

You have two people in the center of an endless plane. Each one is holding some item that can fit in their palm, like a tennis ball. Both persons are identical in physical ability and brainpower. ...
3k views

### Who is the killer [closed]

A man was murdered in his office bathroom. Detective Troby found a paper with alphabets written as below from the pocket of the dead man's corpse. ...
3k views

### What is twice the answer to this question? [closed]

What is twice the answer to this question ? Just thought some people here would like this brain-teaser ;)
5k views

### The treasure hunt

An archaeologist who has just unearthed a long-sought-after pair of ancient treasure chests. One chest is plated with silver and the other is plated with gold. According to the legend one of the ...
670 views

### Find out which instruction is wrong

The object of the following flow-chart is to rearrange the numbers in boxes 1, 2 and 3 in such a fashion that, at the end: ...
231 views

### The hour glasses! [duplicate]

You have two hour glasses: A seven minute one and an 11 minute one. Using just these two hour glasses, accurately time 15 minutes.
399 views

### The 'number of months' challenge [closed]

Okay, here I am having a puzzle for you all. The puzzle is quite short and clear in it's own way I am telling you. Rather than a question it's more like a challenge to you all (answer is already known)...
4k views

### So how did the date go?

It's Monday morning. Fernando just sat down at his desk for another hard day at work - programming stuff and answering telephone calls - "have you tried turning it off and on again?" As he is about ...
2k views

### Irreversible body swap

In Futurama's episode 6x10, the professor invents a device which allows to switch mind between two bodies. He then switches his mind with Amy. It later turns out that the a given pair of bodies can ...
2k views

### Knights and knaves in a foreign language

You die and ascend to heaven, there is a knight (truth-teller), a knave (pure liar) and a joker (random) sitting on a cloud - they all look the same. In order to gain entry you must determine their ...
942 views

### Generalized Path Guards

Suppose you are traveling and come to a fork in the road. One of them leads to something good like a cat shelter and a company handing out free ice cream and money, while the other leads to something ...
1k views

### The antisocial chair problem

A room has n empty chairs in a row. You choose a chair and sit it in it. Now someone else comes in and sits as far away as possible from everyone in the room or an arbitrary choice of furthest chair ...
3k views

### Why was the Five Star Hotel sued? [closed]

In a five star hotel, I ordered for a cup of coffee. When I was about to sip, I found a fly in the coffee. I complained. The manager apologized, took back the cup and brought another fresh hot one. ...
722 views

### Two Armies of Ants

I saw this puzzle a while back in a children's puzzle book, but I'll try to make it as accurate as possible. There is a small army of three ants walking down a very narrow road, so there is only ...
544 views

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### 16 Buttons, Turn them all Red or Green?

There's 16 buttons arranged in a 4 by 4 square. They are coloured either red, or green. They appear like this (red being 1, green being 0) 1010 0101 1100 0011 Each press will switch all the ...
8k views

### How do you solve a word puzzle when you have no idea where to start?

When you're looking at a logical word puzzle, what sorts of clues should you try to look for to solve them? There have been quite a few puzzles posted to this site so far that I spent a few minutes ...
2k views

### Banana? Or Orange?

25 kids were in a class, they were all trading lunches. Each kid traded their lunch 5 times. At first 12 kids had bananas. At first 13 kids had oranges 16 kids like bananas 14 kids like oranges In ...
2k views

### The way to Acarien puzzle

You are on a quest to the find the lost kingdom of Acarien. On your way, you end up at a fork in the road. Both paths look exactly the same. At the junction sits a wise man. The wise man will only ...
840 views

### Way to memorize shape - number combinations in short time [closed]

A visual memory test application gives some time to memorize images - numbers combinations, after that it shows a random shape and asks what the number is. What is to trick for such an application if ...
5k views

### Poisoned Bottle of Wine! [duplicate]

This puzzle is taken directly from a site and reworded. The site can be found at the bottom of this question. You are king of an empire and you are going to have a party soon. The party is the most ...