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
12answers
6k views

Not enough pylons!

Bob is a temp working with a construction company in repairing roads and barriers. One day Bob got called up to repair a barrier along a strip of highway. Bob will need 100 "Company X" pylons to ...
-4
votes
6answers
9k views

Fit ten horses in nine boxes [closed]

Here is my puzzle: How can you fit ten horses in nine boxes? Here are the boxes: Rules: All boxes must be filled No additional boxes can be created Good luck :)
21
votes
5answers
7k views

Which is worth more - a chest of nickels or half a chest of dimes?

I have two large identical chests of exactly the same shape, volume, etc. One is completely full of nickels (each worth 5 cents), and the other is exactly half full of dimes (each worth 10 cents). ...
2
votes
1answer
509 views

What does this mean?

What is the magic word? 011021042021011012012032012032014 Clues (Read, in order, one and re-think the problem): Five letter word 'A' equals 011051 Binary (Eight digit per) Compressed ...
-1
votes
2answers
5k views

Can you make 2 squares and 4 rightangled triangles using only 8 straight lines? [closed]

Can you make exactly 2 squares and exactly 4 right-angled triangles using "only 8" that is exactly 8 straight lines? I am looking for 3 different answers.
23
votes
4answers
3k views

Connect the Pipes

Each pipe shown on the left (A through I) connects to exactly one pipe on the right. To hide the answer, I have put a curtain over the pipe crossings and grayed out the pipe colors on the right side. ...
9
votes
1answer
3k views

Upside-down numbers differing by 78633

When I acquired my Mercedes-Benz car in Germany, the first thing I had to do was to get a license plate. The plate I got had a peculiar number on it. It consisted of 5 different numbers and by mistake ...
1
vote
1answer
307 views

Which one is the road (or path) to Beijing? [duplicate]

If I remember correctly, this is a question for admission to a college in China long time ago: 1) You are traveling and have reached a point on the road where it diverges to Path A and Path B. One ...
10
votes
1answer
549 views

Do I feel lucky? Well, do ya, punk?

Two Pepperbox Pistols, a Lemat 1861 revolver, a Winchester Model 1873, a Colt Thuer Derringe, two Colt 1860 Army, a Smith&Weston Model 1 1/2, a Coach Gun, and a Double Barreled Shotgun. 10 dead ...
13
votes
2answers
3k views

The broken window

A window was broken in my house and I need to find out who did it, can you guys help me? When asked who did it my friends replied with the following in order starting with 1: "I didn't do it" "1 is ...
5
votes
1answer
818 views

Kill the jokers! - Part 2

The famous and ruthless explorer Wyoming Wilbert reports in the third part of his memoires that he once visited an island inhabited by jokers and truth tellers. Truth tellers always tell the truth, ...
7
votes
11answers
3k views

121 coins and a balance

Inspired by this puzzle... You have $121$ apparently identical gold coins. At most one of these is fake, and weighs a different amount than a genuine coin. In front of you is balance with two pans. ...
7
votes
17answers
18k views

Measuring the amount of liquid in a container without a measuring tool [closed]

The Problem Let's say you are asked to measure the amount of liquid in a container, but you are not allowed to use any direct measuring tool (such as a balance, ruler, or anything of the sort). You ...
4
votes
2answers
2k views

Determining the pattern of a 3x3 grid of hidden black and white tiles by revealing only two

I was playing a game called Space Rangers earlier, and stumbled upon a "text-adventure" mission in it, which required me to find what's supposed to be the only possible solution to this puzzle. I ...
12
votes
1answer
1k views

Diabolical dice!

I have two 6-sided dice which between them have 12 different numbers, but some of the numbers are hard to tell apart because one is the same as the other upside down (like $89$ and $68$). I throw the ...
2
votes
1answer
1k views

The 5 card problem with 2 prisoners [duplicate]

Note: I found this puzzle on quora. I don't have a solution for it. I couldn't find it referenced using google search. This time the jailor gives two of his favourite prisoners a chance to escape. ...
3
votes
3answers
460 views

Magic cutting squares with given sum

You meet a guy on the road. The following conversation follows: He: Let's play a game. Give me any natural number from $3$ to $10$. I'll call this number the grid size You: Okay, $4$. (...
4
votes
2answers
129k views

Brooklyn Nine-Nine Riddle: Weighing Islanders [duplicate]

A brain teaser posed by the character Captain Ray Holt of 'Brooklyn Nine-Nine' played by Andre Braugher during episode 18 of season 2: "There are twelve(12) men on an island, eleven(11) weigh ...
1
vote
2answers
1k views

What color is the statue? [duplicate]

This question has been tagged as duplicate of Two doors with two guards. What makes this questions different: Let me state the obvious about this question: you meet one islander. you ask one ...
1
vote
1answer
671 views

What is the next number in this puzzle [duplicate]

What is the relationship of this sequence and what is the answer for the last? 0001112359 = 4 1887145865 = 7 5528695874 = 6 0000085021 = 8 3247514251 = 0 5847962150 = ?
3
votes
2answers
1k views

Coin division puzzle [duplicate]

You are blind and sitting at a table with 100 coins on it. You know exactly 50 coins are showing heads and the rest tails, and you can tell by feel where the coins are, but you are unable to see or ...
12
votes
1answer
731 views

Jack Sparrow and The quest for the missing Compass . Part 1

Hopefully this puzzle is not as easy as the last one. Jack Sparrow wakes up startled just when he was deep in slumber, after his night out with the "Ladies". He checks his pocket and finds it empty. ...
8
votes
6answers
1k views

Devious auction game

Saw this on TV today: A man is auctioning a real $20\$$ bill. There are a vast number of bidders. A person may make as many bids as he wants. The starting bid is $5\$$. No $2$ bids must be ...
3
votes
2answers
588 views

How does a common man solve impossibly hard truthteller/falsifier questions?

How does one solve the World's hardest puzzle, and other questions of the type? Is there a proper approach to such a question, or does one just have to be incredibly smart to do so? And here's an ...
92
votes
2answers
39k 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? ...
19
votes
3answers
5k views

Too Many Damn Buffalos [closed]

"Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" The sentence above is an actual sentence which makes perfect sense and is not wrong. The word "Buffalo" has three meanings: ...
-6
votes
2answers
2k views

The Two Identical Twins [closed]

There are 2 twins who think the same, look the same, sound the same, and act the same. The only difference is that 1 of them is male, 1 is female. Without asking the twins for their gender, how can ...
3
votes
3answers
1k views

The Tricky Tunnels!

The king had a mutant rat problem in his kingdom, so he ordered 3 young men to go down under the depth of the ground to find the cause. The 3 young men jumped down the hole, and followed the tunnel. ...
-2
votes
2answers
292 views

You and your “Princess” [closed]

You are an Archer and participating in a tournament. You need to hit the Bull's Eye to win the tournament and the Prize (a big fat pig called "Princess". Wodehouse Anyone?). You love big fat pigs and ...
2
votes
1answer
835 views

What is the equation to solve the puzzle box Super-CUBI 324 step

The Super-CUBI puzzle box takes 324 steps to open or close it, instructions. And uses a Trinary System. It must have a solution as it would be hard to remember all the steps to take to open it. But ...
-1
votes
13answers
2k views

Monkey and the Crocodile

There is a small island in the centre of a lake. The lake has two banana trees. The monkey wants to get all the bananas from the island and so he goes to the crocodile to ask for help. The crocodile ...
1
vote
2answers
580 views

Time Sequence Puzzle (Days)

I found the following problem in a book and don't understand exactly what is being asked. (I) Kamal is available at home from 12 noon to 4 p.m. on Tuesday, thursday and Sunday. (II) His ...
3
votes
1answer
245 views

How can I solve my meditation problem? [duplicate]

I have been given a guide on how to reach satisfaction, and part of this guide requires me to meditate exactly for 90 minutes. I have only been provided 2 oil-soaked ropes which last for 2 hours each ...
4
votes
2answers
465 views

Variant to blue eyes puzzle - selfish logicians

This is a variation of the blue eyes puzzle. Suppose the logicians want to get off the island. They are selfish and think only of themselves. They may help others as well, but solely for their own ...
25
votes
13answers
5k views

3 Planks, 1 nail [closed]

John and Bob were doing some home construction and decided to take a beer break. Before grabbing a seat John pulls out 3 planks of wood, 1 nail and a hammer. John makes a bet with Bob saying I'll ...
0
votes
0answers
75 views

Freedom from the guarded island [duplicate]

You, a well-known submarinist criminal, are taken prisoner in a perfectly circular island, surrounded by water. You stand in the center of the island, with the submarinism equipment (don't worry ...
9
votes
2answers
723 views

Magical Shuffling Hats

As you're walking through the city, a wandering street logician pulls you aside. "Hey, you. Want to play a game?" He rasps in a loud whisper. You, being quite the logician yourself, oblige. He leads ...
-1
votes
6answers
867 views

Copper, Silver and Gold. Who had what?

I made the following riddle in a RPG. Albus, Baku and Croco experimented with some ingots. One was using copper, one silver and the other gold. But none of the experiments worked with the ...
-3
votes
1answer
514 views

3 suspects Logic Puzzle [duplicate]

The following puzzle was posted here, but providing answers to the puzzle was closed without a correct and complete answer being provided: An inspector knows that exactly one of 3 suspects committed ...
3
votes
2answers
668 views

How to generalise Partition of the pie for N envy people?

There is well known task: How to divide a pie between two people, so each will think that he got equal or more that the other one? It has the following solution: I know that it is possible to ...
0
votes
2answers
177 views

Switches and numbers [duplicate]

You have a hundred, labeled, bulbs, turned off and a hundred, labeled, buttons. When you begin pressing the button nº1, all bulbs turn on. When you then press the button nº2 all pair bulbs, begining ...
4
votes
1answer
314 views

Where's that book you want?

A friend of yours, studying law, just walked out of the library and you have a short social talk. During the conversation it comes to pass which books he just returned. One of the books seemed ...
4
votes
1answer
4k views

Is this a correct solution to determining which of two people is the liar using one question?

I was working my way through some Propositional Logic Questions in Discrete Maths by Rosen, when I came across the following question: An explorer is captured by a group of cannibals. There are two ...
3
votes
4answers
734 views

Another poisoned bottle question!

There are $1000$ bottles of wine, of which $n\leq10$ are poisoned at random. (You don't know the exact number) A person consuming the poison dies on the midnight of that day. You have $2$ prisoners ...
4
votes
3answers
998 views

The devils number

You are in a room tied to a chair. The devil tells you that he is gonna ask two groups of 1000 "people" a question and then he will ask you something. If you answer correctly you go to heaven, else ...
2
votes
7answers
2k views

Camels crossing a bridge

Two merchants have 5 camels each. One fine day, one of the merchants sold all of his goods in the market and heads back to the village. He has to cross a bridge to reach his destination, and the ...
3
votes
1answer
1k views

Alphabet Number Matching

If : 888888 = T 777777 = O 555555 = Y 444444 = R then : 666666 = ? Basically you need to tell the logic along with ...
3
votes
3answers
375 views

The salary of three of Alice's coworkers

Alice would like to determine the relative salaries of three coworkers using two facts. First, she knows that if Pauline is not the highest paid of the three, then Paul is. Second, she knows that if ...
-1
votes
3answers
2k views

Using 4 straight lines connect the stars together [duplicate]

Using 4 straight lines connect these 9 stars together without lifting your pen from the surface. The end of each line must be start of the next line.
33
votes
15answers
39k views

Mysterious Murder Mystery [closed]

Last year, December 21, 2013, you were awarded the "#1 Detective in the World" for solving more than 50 murders. Your boss gave you a promotion, contingent upon your moving to Chicago. You agreed and ...

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