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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5
votes
1answer
232 views

Airport Shuttle

A shuttle transfers passengers from 5:30 to 22:30, on a route between an airport and 3 hotels. The shuttle departs the airport every hour on the hour and drops off passengers at the hotels always in ...
5
votes
1answer
185 views

Ultimate Puzzling Challenge: Puzzle A2

Note: story starts here Bob (aka you) happily goes to the challenge organizers, ready to go on. You get a small large note: Hi challenger,Looks like you're on to puzzle A2! This is a bit harder, ...
10
votes
2answers
2k views

My strange friend

One day I was out taking a walk during my lunch and a good friend of mine ran up to me suddenly and shouted "nine!" at me and then pointed at his watch and ran off. Obligingly I looked at the time and ...
2
votes
2answers
259 views

Find all the possible Male Female combination

There are two companies, A and B, which are going to participate in 12 different conferences. We know the output of all the conferences (who will get which desert), based on it find out Male and ...
3
votes
4answers
526 views

Find two numbers based on either their multiplication or exponent

There are two mathematicians with incredibly strong memories sitting in a coffee shop passing the time. Their server proposes a game: First, he gives them a large number: $2176782336$ Then he ...
10
votes
2answers
2k views

When and where was the first logic-grid-based puzzle published?

Logic puzzles with a set of conditions and a "logic grid" are very popular. More than one publisher is currently producing puzzle books with these types of puzzles. A Wikipedia article claims ...
8
votes
2answers
3k views

First day of school

Here's a pretty easy one. A new student (a male) was wandering down the hall of his new school looking for the boys' locker room. He asks a nearby student (who happens to be the school bully) to ...
-6
votes
1answer
337 views

A question about Pinocchio's nose [closed]

What happens to Pinocchio's nose if he says to another person "My nose is about to grow"? Does it grow? Does it stay the same? Something else?
14
votes
9answers
3k views

Red and Blue in the Chocolate Fountain Room

Where: Hackanoogie Prison. When: Who cares? The Master Key Keeper had had a really good day and in a fit of insanity and niceness decided to let all the inmates to go free if they manage to carry ...
1
vote
1answer
339 views

What is my mobile number

10 years ago I met my old friend. He asked me for my mobile and number and I take his mobile and I wrote the following text: waemd.m ph
1
vote
1answer
308 views

Eight Suspects and a Crazy Executioner

A group of 8 suspects; 3 wearing red shirts, 2 wearing green shirts and 3 wearing blue shirts. Eye-witness claims to have seen 3 people in the scene, the shirt of one of them appeared red, while the ...
8
votes
1answer
949 views

World's # 1 painter painted something!

Come one, come all! Gather around my amazing masterpiece and see if you can guess what I painted! I borrowed the following items and took the raw essence of all of each item and made the painting. ...
2
votes
2answers
4k views

The case of the 4 campers and the rickety bridge! [duplicate]

Four people need to cross a rickety rope bridge to get back to their camp at night. Unfortunately, they only have one flashlight and it only has enough battery left for seventeen minutes. The bridge ...
0
votes
2answers
180 views

I need to measure exactly half an hour [duplicate]

I only have two candles, each candle burns for exactly one hour. I do not know the length of the candle. Guessing and estimation is not allowed. You are not allowed any other materials other than the ...
8
votes
3answers
1k views

Forty-six genuine and two fake coins

Inspired by this puzzle. In the country Dragonia, there are only two types of coins: genuine ones and fake ones. All genuine coins have the same weight, and all fake coins have the same weight. It is ...
7
votes
3answers
594 views

What is the minimum number of steps to solve this cloning particles on chessboard puzzle?

I'm creating a puzzle based on the idea from this numberphile video: pebbling a chessboard. You can see a working (yet unfinished) version here. I would like to give the user a feedback of how well ...
2
votes
0answers
365 views

Zebra problem ( popularly known as Einstein's riddle) [duplicate]

The zebra puzzle is a well-known logic puzzle. Many versions of the puzzle exist, including a version published in Life International magazine on December 17, 1962. The puzzle is often called ...
14
votes
2answers
2k views

A Race of Liars

You find yourself in a strange land where a race with five participants has just taken place. Each of the runners is a different age, and each either always tells the truth, always lies, or strictly ...
1
vote
2answers
227 views

A big tennis tournament [duplicate]

We are organizing a tennis tournament. The rules are the default ones. 2 players play against each other the winner advances to the next round this goes on until one player is crowned champion. ...
3
votes
1answer
532 views

Puzzling Pieces of Pumpkin Pi

You bake a nice, delicious-looking pumpkin $\pi$, cut it into 6 slices and serve it on your table. As a fan of numbers, you label each slice with numbers from 1 to 6. Feeling very pleased and ...
1
vote
2answers
3k views

Time Sequence Puzzle

If Thursday was the day after the day before yesterday five days ago, what is the least number of days ago when Sunday was three days before the day after tomorrow? Please explain each step of your ...
9
votes
3answers
580 views

The King's New Accountant

The king of Ebonchester has just returned from his recent conquests of Baronshire and with him he brought four cart loads of plunder. However Baronshire is known for its lacklustre fiscal regulation, ...
1
vote
1answer
219 views

Men and megaphones (with a lot more)

Imagine a grid of infinite size. In each cell can be placed one of three things: A man: who will listen for a sound from any direction and pass it to adjacent* men. A megaphone: which will take in ...
26
votes
1answer
4k views

The tough one from “A Brilliant Young Mind” (2014)

Great movie by the way. I'm quoting from memory, so I may get the wording wrong. The positive integers are each colored Red, Yellow or Green. Prove that for any such coloring, there must exist ...
-11
votes
1answer
410 views

Russian Roulette with a novel twist

The gun is loaded with a single bullet. You go first, and I always win. How is this possible?
7
votes
3answers
37k views

Split 12 liters in half with 5 and 8 liter bottles [duplicate]

You have 12 liters of apple juice in a 12 liters bucket and you want to share it with your best friend. But you have an empty 8-liter and an empty 5-liter bottle. How do you split the apple juice in ...
14
votes
6answers
3k views

To Tell The Truth

Four friends get together. One tells the truth all the time. One lies all the time. One tells the truth on odd-numbered days and lies on even-numbered days. One tells the truth on even-numbered days ...
7
votes
1answer
434 views

Can you find the answer to this algebra equation? [duplicate]

This is an old favorite of mine... Can you find the answer? $(a-x)(b-x)(c-x)(d-x)...(z-x)=?$
5
votes
2answers
865 views

Insert Numbers for equation

this is driving me nuts... Any ideas? Been on it for 2 hours now. The only info given, was this: The solution is not, what you think it is. I guess it is doable with just integers, but every ...
2
votes
3answers
406 views

A game with numbers [closed]

Two people randomly select two different 1-digit numbers (including 0 of course) and calculate their absolute difference. Then They share what they get, What is the probability of having the same ...
4
votes
1answer
1k views

Five Prisoners wearing hats [duplicate]

I stole this puzzle - but I credited it in the source of this question, so if you really want to cheat you can. No cheating, please. There's a penal colony on an island in the South Pacific. It's ...
9
votes
4answers
2k views

Who REALLY killed Derek?

6 people shared a building in London - Lisa the teacher, Caroline the maid, Alice the businesswoman, Thomas the London Underground driver, Derek the coffee-shop owner, and Michael the prison guard. ...
10
votes
2answers
2k views

3x3x3 Rubik's Cube Illegal State

After I learned how to solve a 3x3 Rubik's Cube and a 4x4 Rubik's Revenge, I began challenging myself to solve the cubes to different states rather than the normal solid sides. For instance, I'd solve ...
7
votes
4answers
6k views

Dr. and Mrs. Smith shake some hands

Dr. and Mrs. Smith recently attended a party at which there were 5 other couples. Various handshakes took place. No one shook hands with his/her spouse, no one shook his/her own hand. After all the ...
8
votes
3answers
398 views

Cheryl and her annoying birthday

Remember the 1st Singaporean problem that went viral? Try this! Albert and Bernard just became friends with Cheryl, and they want to know when her birthday is. Cheryl gives them two unknowns: $M$ and $...
5
votes
2answers
535 views

Rainbow Door Sequence

I have 7 doors coloured like the rainbow: You can move in either direction moving one door for the first go, two for the second, three for the third, etc - you get the idea. NOTE You can jump to ...
6
votes
2answers
744 views

Cultural Patrimony

Few month ago, I was on vacation visiting an old friend in his own country. We were sitting on his balcony enjoying the sea view from up the hill and listening to his old favorite music when he asked ...
5
votes
1answer
504 views

What is the best name for true-tellers, liars and normals

In the world exists a lot of puzzles based on variations of true-tellers, liars and normals (sometimes lies, sometimes not). There are plenty of names for these characters, for example see the ...
47
votes
4answers
5k views

Batman and the piano

Batman: Alfred. Are you there? Alfred: Yes, Master Bruce. How may I help you? Batman: ...
5
votes
2answers
2k views

Connect the colored dots

I've got this: By connecting the dots, I get this: Could you do the same for this one: There is a unique solution. The rules are: You have to use every square, lines can't cross each other and you ...
7
votes
5answers
2k views

Maths Puzzle ABCDE

Replace the letters $A$, $B$, $C$, $D$, $E$ with the numerals $1$, $2$, $3$, $4$, $5$ such that the following equation is true: $$AB*C=DE$$
1
vote
1answer
853 views

How many doors are there? [duplicate]

You wake up in the center of a large, homogeneous, nearly-circular room. Along the edge of the room, are many doors, each looks identical to the last. When you stand at one door and look across the ...
25
votes
1answer
2k views

Four is Cosmic!

This is a little puzzle I heard a while back from one of my mathematically inclined friends- I get the sense that it's bounced around a little, so forgive me if you've heard it. There is a sort of ...
2
votes
3answers
3k views

Every number eventually equals 4 [duplicate]

This is my first Puzzle posting on here. If I can figure out how to do a spoiler, I will add in a hint. Best of luck! I heard this one a while back, and I don't know how well known it is. Example 1: ...
6
votes
1answer
437 views

Help - I lost my password

I lost my password to a critical website. All I have is a really obfuscating password hint. Can you please help me figure it out? My password hint: Third letter is r, middle is a. In my email I ...
10
votes
3answers
2k views

The Expedition Into The Ancient Cave

You are a archeologist and have taken 8 of your students on a expedition trip to a ancient cave to try and find ancient treasure. After you and your team entered the cave, you travel as a group ...
2
votes
1answer
1k views

The 100 Hat Riddle [duplicate]

I saw this riddle ealier today on 9GAG (and it's found on multiple news sites), Im not quite sure about the answer, but i'm wondering if someone can solve it. 100 prisoners are lined up by an ...
32
votes
4answers
13k views

Honest Monk Puzzle

Suppose you are on an island with 32 monks and you are told that one of the monks is always honest. Every day the monks say whether it is going to rain. You are required to say whether it is going to ...
7
votes
0answers
249 views

The Switch Riddle [duplicate]

I saw this riddle ealier today on 9GAG (and it's found on multiple news sites), I have found 2 answers with my collegues, but i'm wondering if someone else can solve it. 'One hundred prisoners have ...
7
votes
1answer
664 views

Bottles of wine, poisoned with time

You are the ruler of a medieval kingdom. This time, you've decided to throw a royal party with 10,000 bottles of wine, rather than just 1,000. You remember the problems the courtier gave you with the ...

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