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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10
votes
5answers
396 views

2 fake coins from a pile of 30 coins

You need to find two fake coins from a pile of 30 coins. You know that a fake coin has a different weight to a real coin, but you don't know whether it is lighter or heavier. You also know that all ...
13
votes
12answers
2k views

2 Person Same Number Verification

Alice and Beth both receive a random integer from 1 through 10, inclusive. They only know the number that they are given. The two of them want to come up with an algorithm to check that their ...
7
votes
2answers
144 views

Turning a fan on

I bought an air purifier which has [off, low, medium, high] settings and a single button. If it is on, the first button press activates the lights and subsequent presses increment the level with off ...
-2
votes
1answer
117 views

Missing Number Picture Puzzle

This is is logical reasoning puzzle in which your challenge is to find the relationship among the given numbers and then find the value of the missing number. Source: https://www.funwithpuzzles.com/...
8
votes
5answers
2k views

Three 50/50 guesses

Three friends enter a quiz-show as a team, the final round of the show is all or nothing, they only get their prize if they can win this round. Three boxes labelled 1, 2 and 3 are placed in a room, ...
8
votes
3answers
1k views

30 fake coins out of 99 coins v2

Follow up question to my other question, but totally different methodology required. You are given 99 coins which consists of 30 fake ones. You also have a digital balance scale with perfect ...
8
votes
0answers
404 views

An enrypted clue for the police

A well known German drug dealer contacted his accomplice with an encrypted note. The police caught the accomplice during a drug deal and found the note in his backpack. Note: (For those who can't ...
9
votes
1answer
296 views

Grid Deduction Deduction: Cave or Tapa?

The following grids can be solved using either Cave or Tapa rules. First, determine what kind of puzzle each grid represents. (They can both be of the same kind, or there could be one of each kind.) ...
8
votes
2answers
1k views

Dodgy Dies: The Puzzling Premiere

Inspired by the "Treasure Hunter Monolith" minigame from Danganronpa V3 Dodgy Dies Guide Terminology Block - a single die on the grid. Cycle - a list of blocks Value - the ...
14
votes
9answers
3k views

Which person is telling the truth?

A person was killed. There are 4 suspects. A says C is the killer. B says C is the killer. C says that B is lying. D says that it wasn't him. There is only one person telling the truth. Who is this ...
6
votes
3answers
1k views

Zombie horde incoming! [duplicate]

Here is a puzzle I found on youtube's Ted-ed channel and found quite fun to solve. You and 3 more people are for some reason running away from a horde of zombies in the darkness while holding a ...
9
votes
1answer
409 views

Cryptic Battle: Welcome to PSE!

Inspired by jafe's Double feature series. The following is a hybrid Star Battle and diagramless cryptic crossword. Solve the clues and the grid, then place the clued words in the grid in a logical ...
117
votes
7answers
42k 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?
1
vote
1answer
423 views

Several IQ test puzzles

Here are some fun puzzles I would like to know the answers and explanations for. Enjoy! Source. 1. 2. 3. 4. 5.
5
votes
2answers
626 views

Is there a way in which all the members can be seated?

Here's a puzzle where it is very difficult to find a possible seating arrangement of all the members. I have been struggling to solve it. I have devoted so much of my time trying to figure out ...
6
votes
1answer
565 views

Super Secret Cookbook

You requested the password for a super secret cookbook and received an SMS with the following content: 77733666688833 2555555 777772222337777 2663 777337555222233 84433 6688622337777777 9444844 ...
16
votes
1answer
484 views

Octagonal Kurotto

This is a Kurotto puzzle. Rules of Kurotto: Shade some cells to form connected groups of shaded cells. Circled cells are unshaded. If they have a number in them, that number tells you the sum ...
3
votes
0answers
206 views

The Weird cipher password?

During your search to the ' great hidden computer virus ' , you realized that you are just a password from accessing it. Frantically , you searched for a clue that might help you . At last you ...
0
votes
0answers
47 views

Is it necessary to state that there is a logician with a blue hat in this 100 logicians puzzle? [duplicate]

I've been discussing the logic puzzle where 100 logicians, all wearing blue hats, are trapped in a room and told: they can leave when a bell rings if they know they know they are wearing a blue hat, ...
4
votes
3answers
568 views

Carousel Seating Logic Puzzle

Puzzle from my good friend and fellow Sporcle user, AuroraIllumina! Eight children are riding the carousel: four girls (Anna, Beth, Claire, Diana), and four boys (Eric, Frank, George, Henry). It is ...
20
votes
3answers
2k views

Can you put L trominos to fill the figure?

In the above picture, there are 24 squares. Can you only use L trominos to fill the figure? If yes, give an example. Otherwise, please explain why. An L tromino is like this:
6
votes
4answers
857 views

Knights and Knaves in the Wild West

Late at night at a bar in the Wild West only two cowboys from out of town are left, playing poker with the barkeeper. One of them cheats, so another throws over the table and they have a fistfight (...
43
votes
11answers
8k views

3 doors, three guards, one stone

You are in a room with three doors. Behind two of them, the darkest pit of hell waits for you to make a mistake. The other door leads to heaven and freedom. Each door is guarded by a guard: Michael, ...
5
votes
1answer
235 views

Identify the Drink Given Other Info

There is a smooth dance, a ball sport, a country's capital, a month, and a drink. What's the drink?
10
votes
4answers
684 views

Sharing cake among 9 or fewer people

You are expecting guests to your birthday party. You know that there will be at most 8 guests, but you don't know how many will actually come. What is the smallest number of pieces you should divide ...
9
votes
5answers
3k views

A simple murder mystery puzzle that I came up with

A woman was found dead in her apartment. She was hanging from the ceiling but the detectives deduced that it was not suicide because of the bruises on her body (indicating a struggle) and the mess in ...
12
votes
3answers
2k views

Can you catch the thief?

This was a puzzle I recalled from university a couple of years back. I don't know what the original puzzle is but if someone knows it, please let me know so I can credit the source. You are a police ...
13
votes
8answers
4k views

2 Guards, 3 Keys, 2 Locks

There are 2 guards: one only tells the truth, the other only lies. There are 2 locks and 3 keys: each lock can only have 1 key matched - the 3rd key doesn't do anything. You can only ask one ...
11
votes
2answers
1k views

The three greedy pirates

Her eyes lit up as the pirates Sparrow, Barbossa and Turner opened the treasure chest and saw the mountain gold coins. After pirate's tradition, Sparrow first took a coin, then Barbossa two, ...
11
votes
3answers
666 views

Twelve Labours - Prologue

This puzzle serves to introduce the ‘Twelve Labours’ series of puzzles. Its solution is standalone and does not contribute to the meta-puzzle at the series end. “Wake up, wake up, wake up! What are ...
4
votes
2answers
235 views

How many different Paths exist in this journey?

Rules: 1. Start from point A reach back to point A. 2. Each path needs to be visited at least once and only once in each journey. 3. never turning off at crossroads. to make it more understandable ...
11
votes
3answers
2k views

Find number 8 with the least number of tries

You and your friend plays a game. In this game, there are numbers written on the cards from 1 to 12 on one side (so 12 cards in total). The other side is blank. You can write anything on the blank ...
7
votes
4answers
392 views

Island of Knights, Knaves, Spies

There are 3 types of inhabitants of a village: knight, knaves, normal. You should map each inhabitant with its type, by asking only this type of question to a person: "Hey X, what is the type of ...
7
votes
5answers
952 views

The travel to a friend

You want to visit your close friend in the city Averola. For the long travel you brought your dog with you. Unfortunately, the guards in front of the gate to the city won't let you through. One of the ...
8
votes
1answer
221 views

A Problem of Succession

In the kingdom of Puzzlevania, the old king has recently passed away. And, what's worse, he left the following instructions to his five children (In order of age: Anne, Barry, Charles, David, and ...
3
votes
1answer
178 views

A village with not enough resources

Village Morental Population: 20 You: a visitor The village doesn't have enough resources for 20 people. The king decides to ban 10 villagers from the village. The king is not ruthless, so he gives ...
8
votes
2answers
514 views

How many people are there?

This is a variation of an old puzzle. The game starts with several people sitting in a circle, everyone facing the back of another person. They are all wearing blind folds, so nobody can see anyone ...
4
votes
2answers
184 views

Knights and knaves puzzler

A very special island is inhabited only by knights and knaves. Knights always tell the truth, and knaves always lie. You meet three inhabitants: Peggy, Joe and Zippy. Peggy claims, "I am a knight or ...
3
votes
2answers
82 views

Knight and knaves

A very special island is inhabited only by knights and knaves. Knights always tell the truth, and knaves always lie. You meet three inhabitants: Alice, Rex and Bob, where Alice tells you that "Rex is ...
5
votes
1answer
109 views

Find the songs and the event

The ... below refer to songs. Find them, combine them and you get a famous event currently still ongoing. ... can make all this world seem right ... like you want me recognize your age it's a ... ... ...
16
votes
1answer
321 views

Masyu-making game

Two players are playing a game on a $4\times4$ board. The players take turns adding either a white circle or a black circle into any empty square, so that the board makes a solvable masyu puzzle (with ...
12
votes
4answers
2k views

Consecutive numbers that are Manhattan distance 3 apart

Can you place numbers from 1 to 16 on a 4x4 grid, such that the distance between any two consecutive numbers ($a$ and $a+1$) is Manhattan distance 3? Bonus question: can you also make 1 and 16 be ...
5
votes
1answer
304 views

Consecutive numbers that are Manhattan distance 5 apart

Can you place numbers from 1 to 36 on a 6x6 grid, such that the distance between any two consecutive numbers ($a$ and $a+1$) is Manhattan distance 5? Bonus question: can you also make 1 and 36 be ...
6
votes
18answers
4k views

Ask one verbal question to figure out who is blind and who is mute among three persons

This is another "You can ask only one question" puzzle. This is an edited very restricted version There may be multiple answers but I could come up with only one. There are three persons in three ...
8
votes
2answers
303 views

Spiral Stumper Series: Instructionless Puzzle

Spiral Stumper Series is a $5$-puzzles series taken from the Final Round of a local (national) contest, KPK, which has been ended recently and authored by me. The theme is spiral and each puzzle is ...
4
votes
1answer
146 views

Spiral Stumper Series: Ripple Effect

Spiral Stumper Series is a $5$-puzzles series taken from the Final Round of a local (national) contest, KPK, which has been ended recently and authored by me. The theme is spiral and each puzzle is ...
35
votes
10answers
5k views

Knights and Knaves: What does C say?

You are on a fictional island with two types of people: knights who always tell the truth, and knaves, who always lie. Three of the inhabitants - A, B, and C are standing in the garden. A says, "B and ...
4
votes
1answer
170 views

Spiral Stumper Series: Fillomino

Spiral Stumper Series is a $5$-puzzles series taken from the Final Round of a local (national) contest, KPK, which has been ended recently and authored by me. The theme is spiral and each puzzle is ...
1
vote
0answers
75 views

What are my sisters' ages? (With ice cream!) [duplicate]

This is from a book I read as a child. Steve said to his friend Jessica, "I have 3 sisters. The sum of their ages is the same as my age, and the product of their ages is 36. How old are my sisters?"...
2
votes
2answers
123 views

Stuck on a Tapa (variation)

I am stuck on a Tapa puzzle. I have tried solving it a number of times and keep running into the same problems. I am starting to wonder if it is solvable at all. As far as the puzzle itself goes, best ...