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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7
votes
3answers
238 views

Colored items in a box

When I looked in an old box of mine I found the following x items with 4 different colors exactly: 5 items that are either blue or brown. 7 items that are either brown or yellow. 5 items that are ...
67
votes
9answers
479k views

Crack the lock code

Does any one know how to crack this? I got this as a challenge.
10
votes
1answer
3k views

Who is the liar among A,B,C?

Of three persons A, B and C, one always lies while the other two always speak the truth. C asked A: "Do you always speak the truth, yes or no?" A said something that C could not understand. So C ...
1
vote
0answers
43 views

Island Riddle. - How would you approach this and what is your mentality? [duplicate]

There are 12 people on an island. 11 of the 12 people weigh the exact same. However one of them weighs different(more or less you don't know). You have a seesaw. You can only use the seesaw 3 times. ...
179
votes
23answers
81k views

In the 100 blue eyes problem - why is the oracle necessary?

The riddle Randall Munroe (of xkcd fame) has, a bit hidden on his site, a logic puzzle: A group of people with assorted eye colors live on an island. They are all perfect logicians -- if a ...
24
votes
2answers
497 views

A Minesweeper Sudoku

My brother created this puzzle, and he wanted me to post this here. Each 3x3 box contains three mines (those squares also have numbers in them). There are no mines in boxes containing a 1, 2, or 3. ...
6
votes
2answers
211 views

Circle inside circle v2

This question is a kinda follow-up question to: Circle inside Circle You have a large circle with radius $5$ units and you also have a small circle with radius $1$ unit. But this time you have a 10-...
2
votes
4answers
164 views

How to solve this Number Grid?

I have a maths puzzle from a book. It is labelled computation and logic but I cannot make any progress. The book lists the answer and it is valid but I cannot see how the answer can be found. ...
8
votes
2answers
1k views

Largest cages Killer Sudoku

Task 1: Find the maximum value of $n$ for which it is possible to create a regular uniquely-solvable Killer Sudoku (9x9) such that every cage has atleast $n$ cells in it. Rules for killer sudoku ...
10
votes
1answer
508 views

Solution without words

Here comes a series of snapshots in the life of a worksheet that might come into play when solving a variation of a fairly well-known numerical logic puzzle. ­ Parameters of the progenitor puzzle have ...
13
votes
4answers
1k views

Three secret numbers and sum

Three students are given one positive integer number each written on a paper. Every student knows only their own number. Their teacher tells them that the total sum is 16. Later the teacher asks them ...
17
votes
2answers
569 views

What Masyu do with the antique clock?

Anagram is needed, and it will answer: What Masyu do with the antique clock?
12
votes
6answers
2k views

Two men for one gold coin

Two men find an old gold coin and want to have a coin toss with it to decide who gets it. The only problem is the coin is heavier on one side so it comes up heads more than tails. What is a fair way ...
7
votes
2answers
3k views

Alice and Bob play a game

The rain was still falling and Alice and Bob were terribly bored of having to stay inside the caravan, so they decided to play a game. The game is that Alice chooses a number $x$ in the interval [1,n] ...
4
votes
2answers
307 views

Two Truths and a Lie: a logic puzzle

I'm crafting an answer to the game Two Truths and a Lie: each person playing the game says three statements (usually about themselves, though I'm ignoring that requirement for this), two of which are ...
16
votes
1answer
883 views

What is the Color Code™?

Inspired from Can you name the country code? and What is a Number™? series $ \begin{gather} % custom template - reuse if you may \def\S#1#2{\Space{#1}{21px}{#2px}}\def\P#1{\V{#1em}}\def\V#1{\S{#1}{9}}...
0
votes
3answers
134 views

help me please with this question from pdf book for logic tests [closed]

please help find the answer. it says (translation from english to french) complete the missing block with one block from 9 block below.
28
votes
1answer
3k views

Goodbye grand mother <3

My grand-mother died the 17th of June 20 from cancer after spending the last three months nearly alone in her house because of Covid Pandemic. I dedicate her this puzzle. She's Lao and today, for her ...
10
votes
5answers
746 views

Length of an integer is part of its digits [closed]

How many positive integers less than 1,000,000,000 contain their length as part of their digit string? Example: 123466 has a length of 6 and 6 is one of its digits. Hence this number needs to be ...
8
votes
1answer
525 views

Farewell, Barry Poppins!

-"Don't leave us, Barry Poppins!" The adorable Jade and Nigel don't seem to have taken it too well that I'm leaving. They have followed me around my room as I was packing, weeping and ...
6
votes
1answer
218 views

Question which is sort of puzzle from mathematics Exam

I am self studying and trying questions of quantitative aptitude in my mathematics exam and I am unable to solve this problem. Of three persons $A$, $B$ and $C$, one always lies while the others ...
0
votes
1answer
253 views

Math tapestry puzzle #3

Continuation from Math tapestry puzzle #2 Now things are heating up, it looks like this is slowly becoming bigger. I saw my friend Anna working on her tapestry. She asks me, "Do you like it?"...
6
votes
1answer
279 views

A nest of vipers

Somewhere in France, Summer 1858 They invited the priest. Would you believe it? The priest! There is a mirror in the mayor's office. My reflection looks at me with his emotionless eyes, his stiff ...
1
vote
1answer
113 views

Prisoners and their hats [duplicate]

This is a variant some of the existing questions on this exchange, but I can't see this exact problem. Basic example duplicates this question Some prisoners are going to be lined up, all facing ...
12
votes
1answer
623 views

Stuck on a Nonogram puzzle

Help is needed. I have been stuck on this puzzle for some time. Any help or tips would be appreciated.
4
votes
3answers
361 views

Creating the hardest 7x7 maze

This puzzle is based on Creating the hardest 6x6 maze You are given an empty 7x7 grid. You are allowed to paint some of its cells as walls (black), while the remaining cells stay empty (white). A ...
7
votes
1answer
415 views

Sane and crazy persons

I have found this puzzle on internet. 40 persons sit in a round table . All of them are either sane or crazy. When you ask a person "is the person sitting to your right sane or crazy?" a sane person ...
-2
votes
2answers
241 views

Battleship puzzle with no clues

Suppose I have a standard Battleship Puzzle, but with no clues (no square uncovered) at the start. Then I'm given 5 "fires" that uncover a square, what would be the best strategy to chose a square to ...
5
votes
4answers
634 views

Can't figure this one out.. What is the missing box?

I've been stuck on this for ages, and can't figure this out. What is the missing box, and the logic behind the answer? This was taken from a Korn Ferry Leadership Assessment practice trial.
5
votes
4answers
301 views

Cattell IQ Test

Some of Cattell IQ Tests really stuck me. So I hope you can help me. In these two tests, which one is true according to the logic? And in this one, we find two odd pictures, probably some kind of ...
8
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 ...
26
votes
1answer
1k views

Hey, This is a 100th Puzzle of Mine!

Yep, this is my 100th puzzle here in PSE~ I'm really having a wonderful time here, thank you so much guys! >< I planned to write a harder and bigger one, but it turned out I was too lazy to do that....
15
votes
4answers
2k views

Creating the hardest 10x10 maze

You are given an empty 10x10 grid. You are allowed to paint some of its cells as walls (black), while the remaining cells stay empty (white). A robot is programmed to start in the top-left corner of ...
2
votes
1answer
93 views

How to understand this line in the solution to this puzzle?

I'm trying to understand the solution to a puzzle named "Expelled," the link to which is here. Most of the solution to the puzzle makes sense to me, except the most important part -- how to determine ...
3
votes
1answer
101 views

It's all in the 2's follow-up question

This is in regards to the solution in Slitherlink - It's all in the 2s I know it may seem dumb, but I don't understand the logic behind the second 2 chain in the solution. To help provide clarity ...
9
votes
2answers
174 views

Cut It Up! (then find a phrase)

This is a "sorry for messing up yesterday's clues" puzzle. For each shape below, divide along grid-lines into identical pieces (rotation and reflection allowed). The first shape has 3 pieces, and the ...
12
votes
1answer
502 views

Slitherlink - It's all in the 2s

Can you solve this Slitherlink puzzle that I came up with? And in CSV: 3 - 3 - 2 - - 2 - 2 - 2 - - 1 1 2 2 1 - - 2 - 2 2 - - - 2 - 1 2 - - 1 - I tried to ...
26
votes
4answers
4k views

Creating the hardest 6x6 maze

You are given an empty 6x6 grid. You are allowed to paint some of its cells as walls (black), while the remaining cells stay empty (white). A robot is programmed to start in the top-left corner of the ...
48
votes
10answers
4k views

Clever Jack - A logical fairy tale

As so often happens in fairy tales, there once was a king who had an intractable problem, one that even his wisest advisers could not solve. After many years of frustration, the exasperated king ...
16
votes
9answers
4k views

Three boxes, Four questions, Three times not true, Once the truth

There are 3 boxes, only one of which contains a treasure. The guardian will only answer you truthfully once, the other three times he will lie. You may ask 4 YES or NO questions. Which questions ...
1
vote
2answers
328 views

The Missing House Number

The Visit One day I was visiting my sister in Boston and heard a bunch of kids yelling and playing in the yard ( yahd ). I couldn't see the kids, and hadn't seen my sis for years so I asked her, "...
5
votes
3answers
1k views

Puzzle to test IQ

I've been figuring for this quite some time. Hope someone can help me out.
11
votes
3answers
261 views

EDUCATION becomes a pandigital number

Each of the letters of the word EDUCATION is assigned a different integer value between 1 and 9, for a total value for the word of 45. With the same value for each of the letters, the total values of ...
15
votes
3answers
315 views

Curve Data: A-hint for A-thin

I just recently know about Curve Data puzzles from Logic Masters India. Here I tried to write two simple puzzles to introduce them to you. They should be easy though as I still can't write a harder ...
2
votes
1answer
271 views

What is the solution to this matrix reasoning puzzle?

It is from http://www.programaths.com/iqchallenge/index.php And one of the last items i didn't have any clue what is the solution I know the answer but the solution and the reasoning to it i can't ...
23
votes
2answers
1k views

New logical puzzle

The goal is to divide the grid into regions of exactly four cells (tetromino). Each region contains exactly two different symbols. Regions of the same shape must contain the same symbols. The ...
3
votes
4answers
201 views

Mensa Pattern recognition riddle

I have a question about the solution of this pattern recognation task: I know that according to the book where I it found the correct answer is E. The "argument" is: Vertical lines represent $1$ ...
8
votes
4answers
437 views

Reconstructing the results of a 4-team soccer tournament

4 teams play in a "round-robin" soccer tournament, in which each team plays each other team once. Each game has 3 possible outcomes: team 1 wins, draw, or team 2 wins. The winning team receives 3 ...
6
votes
1answer
374 views

My friend's dad gave her a puzzle to solve, and I've never seen anything like it, any help would be greatly appreciated

I am admittedly not a puzzle person, but I have never seen anything like this, and I am at a complete loss. I have spent an embarrassing amount of time on some weird theories. Any help would be an ...
29
votes
2answers
1k views

Reverse Puzzling 2

This puzzle was inspired by Dr Xorile's first reverse puzzle! Kudos to him for coming up with such a fun format. Intrigued, I gave George yet another famous puzzle to ponder over. Once again, I was ...

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