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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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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
458 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, $4$. (...
3
votes
2answers
119k 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
656 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 = ?
13
votes
9answers
13k views

They use me… What am I?

I'm complex inside,but easy on the outside. I'm loud for one,but quiet for others. I'm used to getting hit,but there's no alternative. I die as fast,as I rise again. What am I?
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
718 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
584 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 ...
90
votes
2answers
38k 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? ...
20
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
289 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
802 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
541 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
244 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
452 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
722 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
843 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
497 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
667 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
724 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
984 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
1k 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 ...
13
votes
2answers
929 views

Devising a sudoku where the rows are the moves for a draw in tic tac toe

The task is to construct a sudoku whose rows (or columns) are the moves for a game in tic tac toe where the game ends in a draw. Here are some clarifications and constraints which should limit ...
-4
votes
1answer
264 views

Timetable Planning [closed]

There are 16 seminars with the following durations in minutes: 60,45,30,45,45,30,30,45,60,60,45,30,30,60,30,30 They need to be divided into groups. Each group must have 2 subgroups. The first ...
5
votes
1answer
465 views

The Final Question of MU episode 1

I played this puzzle game, the last question of which leads to this website, which contains, hidden as a comment in its HTML, the following string: OgUMGU0EHk0ZBQwZTQMCBB4ITSwqLCQjUgo= Believing ...
4
votes
2answers
1k views

What is the maximum number of cities that can be destroyed?

As a commander of an army battalion, you have to plan the attack on some enemy cities which are connected by road-network. Before starting the attack, you have information about all the cities and ...
33
votes
9answers
6k views

Find the composite poison in the wine bottles

You are the ruler of a medieval kingdom who loves throwing parties. The courtier who tried to poison one of your wine bottles last time was furious to learn that you managed to identify which bottle ...
3
votes
1answer
518 views

Evaluate the long multiplication

Evaluate Q1:$[-100\times (-99)] \times [-99 \times (-98)] \times [-98 \times (-97)]..... (97\times 98)\times (98 \times 99) \times (99 \times 100)$ And Evaluate Q2:$(-100-98) \times (-99-97) \...
7
votes
1answer
2k views

Eight animals are sitting around a circular table

Eight animals named E, F, G, H, J, K, L and M are sitting around a circular table facing the centre. These are the kinds of the animals: Cat, Cobra, Dog, Elephant, Falcon, Llama, Panda and Sparrow (in ...
11
votes
1answer
823 views

The completely generalized poisoned-bottle problem

Since there have been quite a few poisoned-bottle problems posted to the site already, I thought I'd post a general formula to cover all future variations of this problem (at least where a single ...
4
votes
3answers
412 views

$n$ monsters and $n$ people

There are $n$ monsters (M) and $n$ people (P) on the left side of a river. Nobody is on the right. They have a boat that can hold up to 2 beings. At no point on time may either of these be true: $$M_{...
4
votes
1answer
473 views

Where did you end up? [Part 1]

Follow the clues and tell me where you are in the end. PSE To the opposite of the opposite of 2 + 2 ~= 4 Go to the way you round .5 If up is down and down is up go down ...
4
votes
4answers
728 views

A village of pick pockets!

There is a small village of 100 people. An unknown number of these villagers are pick pockets. Each day, you're allowed to take as many villagers as you wish out of the village. When a pick pocket has ...
8
votes
3answers
2k views

In the blue-eyes puzzle, why can't they skip ahead? [duplicate]

In the solution to the Blue Eyes logic puzzle, there is a follow-up question: Each person knows, from the beginning, that there are no less than 99 blue-eyed people on the island. How, then, is ...