Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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).

4
votes
1answer
737 views

Am I allowed to use the XOR operation for the “Three Gods Puzzle” AKA the “Hardest Logic Puzzle”?

So I wanted to ask something about the Three Gods Puzzle which you can read more about from here: https://en.wikipedia.org/wiki/The_Hardest_Logic_Puzzle_Ever Basically, the question of the puzzle is: ...
5
votes
2answers
464 views

The Grand Heist

One day, the police receive an anonymous tip that a robbery is about to occur on the fortieth story of a tall building. They grab a car and drive as fast as they can to the site. On arrival, they ...
17
votes
1answer
275 views

Diabolical Deceptions: A 333rd Birthday Tribute to J.S. Bach

Johann Sebastian Bach is one of the most famous composers from the Baroque period. If he was still alive today, he’d be 333 years old. So, let’s celebrate 3 of his most famous works with a 33x33 loop ...
-4
votes
2answers
182 views

Come on people! what am I? [closed]

You are in a store when out of nowhere you hear a voice. It asks. what am I? It follows the question with a story. I asked a lady before and she said “I think you are a banana?” then I ...
2
votes
2answers
142 views

The Inducheon Conspiricy (Who is guilty #8)

At the Korean Nation Police Agency (NPA) in Migeun-dong, Seoul, researchers discovered that 73% of the Senior Inspectors (경감, 警監) all came from the small village of Inducheon. At first, they thought ...
0
votes
4answers
194 views
-1
votes
2answers
111 views

who eats more fruits? [closed]

in a party 3 brothers discussing: first brother says " I ate more fruit than 2nd brother and 2nd brother ate more fruit than 3rd brother" 2nd brother says " 3nd brother ate more than me also 3rd ...
3
votes
2answers
272 views

The Multiple Choice Test Test

One day, the logic professor announces a pop quiz. "All questions in this test are about the test itself. In fact, the test is open note since you have a copy of the test itself. Good luck!" 1. What ...
2
votes
0answers
140 views

banana at party [closed]

At a party, three boys ate bananas. First boy: I ate more than second one and he ate more than third one Second boy: Third one ate more than second one and me Third boy: I ate the same ...
8
votes
2answers
533 views

Hat Puzzle with 5 different colours and 3 people

A dad wants to play a game with his 3 children this Christmas. He has a bag with 5 hats; 1 white, 1 yellow, 1 red, 1 blue and 1 black in it. The hats are all equal except their colour. He will place ...
4
votes
1answer
435 views

Lewis Carroll's Logic Problem #1, page 386

This is one of Lewis Carroll's logic problems for which no solution was given. I have reached a solution and am looking for someone to confirm it. This problem is taken from William Bartley's book "...
0
votes
1answer
156 views

Most efficient way to travel home for the Holidays? [closed]

A group of ten students needed to travel home for the Holidays. Not more than three of them live in the same town. At least two of them would like to visit their fellow classmates. One of them has a ...
3
votes
4answers
360 views

Horse Puzzle again

Given 8 horses and you can race any 5 of them and after every race you get the 2nd and 3rd fastest horse how would you find the fastest horse in minimum number of steps. Well the minimum number of ...
7
votes
1answer
501 views

What is the Unit Digit of the Sum?

I am thinking of 2 integers $x$ and $y$ which follow the following; $$2≤x≤y$$ $$x+y≤47$$ I then write the sum $S = x+y$ and the product $P=xy$ on two separate cards. I pass the sum card to player A ...
1
vote
2answers
195 views

A couple of couples

Two couples have babies simultaneously in different hospitals. They don't know the expected gender, and each have one child which is F or M. How can they arrange in advance, given a guess each on ...
4
votes
2answers
244 views

5 Digit Code Puzzle

We have a 5 digit code, any place can take 1 2 or 3. How do I find where the 2 is placed (if placed) knowing this criteria? 1) If the 1st digit is not a 3 then the 2nd is. 2) If the 1st ...
3
votes
1answer
119 views

Triskadecimal Emojis

[This puzzle is heavily based on one from video game Zero Time Dilemma.] I have one of those weird individualist friends--to give you an idea, he spells his name H-E-N-🔟-R-Y. ...The 🔟 is silent, y'...
1
vote
2answers
104 views

Intuition or Approach for this problem [duplicate]

Assume you have 8 horses and you can race any 5 of them at time. After every race you get the 3rd and 4th fastest among them. How will you find the fastest among them? What would be the general ...
5
votes
7answers
1k views

9sums - a logical deduction puzzle

Each set of minuses contains an integer in the range [1,5]. The given numbers are the sum of the surrounding 4 numbers. --- --- --- --- 13 14 11 --- --- --- --- 11 ...
6
votes
3answers
453 views

Monty's Labyrinth

(A fun combination of two classic puzzles, hope seasoned puzzlers enjoy.) Having escaped through almost all of a labyrinth, you are met by three magical doors. Two of them lead to certain and ...
-3
votes
2answers
421 views

Brain Testing Logical Reasoning Puzzle

Can you answer this logical puzzle? Puzzle Source: https://www.funwithpuzzles.com/2018/12/brain-testing-logical-reasoning-puzzle.html
3
votes
1answer
251 views

Applied logic challenge problem #2

This is similar to my previous Applied Logic Challenge Problem but with a significant difference at the end which could make this problem somewhat more difficult. Again it is a problem of my own ...
2
votes
1answer
95 views

14sums - the diamond standard

My initial question had lots of answers, and my second had too many constraints. So, I have removed some constraints and added another. Same rules as before, but we are now using $[0,6]\cap\mathbb{Z}$....
5
votes
1answer
160 views

The Inducheon Conspiracy (Who is guilty #7)

At the Korean Nation Police Agency (NPA) in Migeun-dong, Seoul, researchers discovered that 73% of the Senior Inspectors (경감, 警監) all came from the small village of Inducheon. At first they thought it ...
4
votes
1answer
218 views

Murder Detective (Who is guilty #6)

[This is a puzzle I've been working on. It has a unique solution. This one is meant to be one of the easier ones. Comments, thoughts and suggestions are welcome!] The suspects are Amos, Celia, Emilia,...
3
votes
2answers
219 views

A Criminal Conspiracy (Who is guilty #5)

[This is continuing from previous puzzles. #4 was quite tricky. This one is meant to be much easier (I'm testing the boundaries here). I've been testing various versions and would love your thoughts. ...
1
vote
0answers
43 views

Sequence puzzle in rows [duplicate]

The below is a number puzzle. It should be read left to right, top to bottom. Question 1: What is the next two rows of numbers? Question 2: How was this reached?
7
votes
2answers
246 views

A Criminal Conspiracy (Who Is Guilty #4)

[Appeal: I'm trying to figure out a fun puzzle formula. There are many out there ("Who owns the fish", sudoku, etc). I'm interested in feedback on whether this works or is interesting for people. ...
5
votes
1answer
130 views

21sums - more constraints

My initial question had lots of answers, as we can practically choose the middle square to be anything we want, and work outwards to the exterior edges, with the corners providing the flexibility ...
1
vote
2answers
4k views

Burning Island - how to survive the fire? [closed]

A man is stranded on an island covered in forest. There are no other humans or animals, he is the only one who lives on the island. One day, when the wind is blowing from the west, lightning ...
-1
votes
2answers
182 views

Out of six numbers in some order, we know third and fourth ranked numbers in every five out of the six numbers. Find the first [closed]

Out of six numbers 1,2,3,4,5 and 6 in some order, we know third and fourth ranked numbers in every five out of the six numbers. Find the first ranked in the order given. for example, if the ranks ...
4
votes
2answers
203 views

Applied logic challenge problem

You must determine what can be concluded from the 60 true statements below. The numbers in each statement represent binary values (true / ...
4
votes
4answers
603 views

How to make both batsmen centuries in cricket match?

This puzzle asked me to in the interview. In a Cricket match, Two batsmen are on 92(on strike) and 99 runs respectively. Three balls remaining and both batsmen make 100 and win the match. Note: ...
9
votes
1answer
297 views

Replace ? by number

This chain of numbers is making confused.Help to find the answer with explanation.
7
votes
1answer
162 views

Relationship between figures

During preparation of a test I am facing problem in solving this non-verbal question. What may the possible solution figure from A,B,C,D?
5
votes
1answer
247 views

Three Triangles by moving two match sticks

Trying two make three triangles by moving only two sticks.
4
votes
2answers
185 views

The bottle(s) of pills of a different weight

I am a laboratory man dealing with random medicine. Day 1 I have 10 bottles of pills. 9 of them contain good pills that weigh 1.000g each, and the other one contains bad pills that weigh 0.999g each....
4
votes
2answers
193 views

Minimal tests for six ethernet lines

I have been wiring my house with ethernet cables, and was testing the connections with a simple ethernet tester: you plug two cable ends into the tester, and it tells you if the cable ends are ...
16
votes
3answers
2k views

Four cups on a table

I didn't invent this myself, I heard it a long time ago and it stuck with me. Four glasses are placed on the corners of a square rotating table. Some of the glasses are facing upwards and some upside-...
4
votes
1answer
150 views

Coloring the Chess Board v2

This is a follow up question to Coloring the Chess Board We have 8x8 Chess board like grid (8x8 2D matrix) and we are trying to color every single square/cell. But the rules are interesting; ...
6
votes
4answers
2k views

Coloring the Chess Board

We have 8x8 Chess board like grid (8x8 2D matrix) and we are trying to color every single square/cell. But the rules are interesting; You may start from any square you want and color that square for ...
0
votes
0answers
194 views

Help me save Christmas - clock and word puzzle

My friend created this puzzle, it tells the Grinch's plan to ruin Christmas. I need to derive the plan from the clocks I have counted that there are 60 words. The clue is that time doesn't go ...
8
votes
2answers
823 views

What's in the mind of the SO poster?

I love the bridge I'm gonna make! This is a SO post. There are not any technicalities involved, you can ignore the code of the declare table insert ..... stuff, and just focus on the dates the OP has,...
0
votes
3answers
158 views

What was in the dead person's bag? [duplicate]

There are two people—they went to the city, and one of them died. The dead person's bag is closed and the living person's bag is open. What was in the dead person's bag?
16
votes
2answers
2k views

Blind Person Ball Game

You are blind and your friend presents you with 6 equal balls of which 3 are red and 3 are green. You friend challenges you to game to find a green ball. You must select 3 of the balls and your friend ...
1
vote
0answers
73 views

What are some good resources to practice logical puzzle-solving? [closed]

I currently own this book called "Algorithmic Puzzles" by Anany and Maria Levitin, and I am having a hard time getting through the higher level problems. I have always been interested in logical ...
23
votes
5answers
5k views

Is there a proof that a map of the United States requires 4 colors?

The Four color theorem states that no more than four colors are required for any map. Can it be proved or disproved that 3 colors can be used for United States map?
7
votes
5answers
2k views

How can the younger one reach Bar Mitzvah age first? [closed]

A Bar Mitzvah is a ceremony which takes place on the 13th year of a Jewish male’s life (to the day). How could it exist that [of two Jewish boys] Jim would be born on the first day of the month and ...
29
votes
6answers
5k views

Who's been stealing Jenny's milk?

Jenny works in an office with four other colleagues and someone has been using her milk. She finds this very annoying as she likes her mid-afternoon tea and she simply can't enjoy the second half of ...
0
votes
0answers
214 views

Mensa IQ test question answer? [duplicate]

What is the missing piece and why? I think it is pretty interesting but I cannot find any pattern. Do you have any idea?