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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Honeycomb puzzle with hexagons

Can you place the numbers 1 through 9 in the honeycomb so that the sum of the numbers in the adjacent hexagons is a multiple of the number in the hexagons? This must be true in all hexagons. The top ...
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8 votes
2 answers
602 views

Pick cards from a table

2022 cards are arranged on the table in front of us. Each card shows a number that we can see. For each of the numbers from 1 to 2022 inclusive, there is exactly one card that depicts it. We have the ...
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  • 135
-1 votes
1 answer
101 views

Is it Ελλάδα or is it Geometry

Here’s the riddle: If taled is a triangle, ip looks like a table, and ix is ( I ) sideways, what is amoge?
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3 votes
1 answer
137 views

Feeding Time at the Zoo - It's Common Sense!

Azeez the Assistant Zookeeper shook his head - "I'll never remember this" "Nonsense!" snorted Jeff. "It's common sense... no two animals eat exactly the same meals and for ...
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0 votes
1 answer
85 views

A barrel contains 10l of whiskey, another one contains 10l of coca-cola. If I do the following operation [duplicate]

A barrel contains 10l of whiskey, another one contains 10l of coca-cola. If I do the following operation in two steps: 1 step) with a glass I transfer 200ml of whiskey from the first barrel to the ...
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  • 325
2 votes
1 answer
71 views

What size square grid can you tile?

A tiling of an n × n square grid is formed using 4 × 1 tiles. What are the possible values of n? A tiling has no gaps or overlaps, and no tile goes outside the region being tiled.
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  • 5,268
4 votes
1 answer
142 views

Show there is always a pair at least 16 apart

The integers 1 to 4 are positioned in a 6 by 6 square grid as shown and cannot be moved. The integers 5 to 36 are now placed in the 32 empty squares. Prove that no matter how this is done, the ...
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  • 5,268
-1 votes
2 answers
137 views

Letters in a Circle [closed]

Bob drew 6 letters into a circle. A, B, C, D, E, F. I don't have a graphic, but imagine those letters into a circle, with A at the top. Bob goes clockwise through the circle, writing every third ...
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  • 109
11 votes
1 answer
212 views

Can I park here?

Help! I visit my mom tomorrow (Tuesday). This parking spot is right across from her house. But when the heck can I and can't I park there?? [ ------ Automatically generated photo description by ...
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4 votes
3 answers
240 views

8x8 Grid with no parallels

In the 8x8 grid graph shown below; you can put points to the edge of grid as shown below (blue dots). The example above has 4 points and you construct a line between two points as shown below; so ...
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  • 28.8k
10 votes
1 answer
733 views

How to solve this Pentomino puzzle?

The following Pentomino board has exactly one solution: The solution is known: I'm trying to solve this board manually, but it is so difficult that I came to believe it is impossible. I noticed ...
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  • 289
5 votes
1 answer
238 views

Problem XXX (Squared) - Number Stile

Happy weekend folks, The intersections of the three circles divide their interiors into seven "regions" By complete non-coincidence, we have seven tiles A "valid" placement is one ...
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5 votes
2 answers
416 views

You are left on a deserted island with 15 trolls

You are left on a deserted island with 15 trolls and you must identify who is who to leave. A tells the truth (truthful) B lies (liar) C always says yes (yes taker) D always says no (no taker) E says ...
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-1 votes
1 answer
142 views

Quite the Namesake

Me and a friend of mine named O were once trapped in a room with a shapeshifter (long story). I had a gun (even longer story), which was good because me and O needed to kill the shapeshifter (possibly ...
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4 votes
2 answers
160 views

Rong-rong (ring-ring variation)

I was thinking about ring-ring puzzle. Suddenly, the 'word' rong-rong came to my mind and made me laugh for no reason. So, I'm messing around with ring-ring rules that fit the rong-rong 'word'. Rules:...
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  • 898
24 votes
8 answers
2k views

N prisoners locked in cells

N prisoners are locked in N separate cells, numbered 1 to N. The warden visits each cell in order with a bowl. Each prisoner can decide whether to put a single coin in the bowl, depending on its ...
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  • 4,169
8 votes
3 answers
929 views

Nights at the Round Table

And there you are, the famous Round Table, seeing it in all its glory makes you smile, even though you thought it was a lot bigger. Well, no matter, as soon as you arrive, you find a parchment on the ...
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  • 4,702
2 votes
1 answer
192 views

Find the arrangement around the octagon

8 people (call them A, B, C, D, E, F, G, and H) are standing on the vertices of the colored octagon below, looking toward the center. E has at least one foot on a secondary color. G is directly ...
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  • 13.3k
1 vote
0 answers
65 views

Attempt to turn all the switches on or off [duplicate]

Here is the puzzle for you. There are four boxes in front of you arranged in a circle. Inside each box is a switch that is on or off. You cannot see inside the boxes. Each turn you stick your hands ...
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6 votes
1 answer
238 views

Bunk-bed Brothers

When we were boys, our mother, because of a shortage of living space, built for me and my five brothers -- Nortie, Matthias, Jack, Kenneth, and Lloyd -- a big, beautiful, sextuple-decker bunk bed. I ...
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5 votes
2 answers
586 views

Next step in this Slitherlink puzzle?

I am playing this Slitherlink app on Android, and get stuck on this puzzle at the following state: I made a lot of progress on the right side, but after this I couldn't find anything that I can do, ...
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  • 3,456
3 votes
1 answer
156 views

Prove that we cannot arrange the cards according to the given rules [duplicate]

There are ten pairs of cards with the numbers 0, 0, 1, 1... 8, 8, 9, 9 written on them. Prove that they cannot be laid in a row so that there are exactly n cards between any two cards with equal ...
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5 votes
1 answer
574 views

A streamer's diet

I'm in dire need of help. I've been hired to take care of a certain streamer during a charity event, but the instructions they gave me for meals and games are just, way too confusing! This one ...
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  • 4,702
18 votes
2 answers
830 views

A Simple Loop with A Poetry?

Who is he really? Please answer this question of mine Starting from the top-leftmost white cell and then You are still going clockwise by Taking the letters where you are turning left but Not, once ...
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  • 33.6k
1 vote
1 answer
262 views

How to solve this North and South Sitting arrangement puzzle?

10 friends A,B,C,D,E,F,G,H,I,J are sitting in a row. Some of them are facing north while others are facing south. Not more than 2 persons facing the same direction sit together. They all have their ...
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7 votes
1 answer
2k views

Is the "rocket" pattern inversible?

The rocket pattern in slitherlink is when a 3 sees a 1 in a diagonal, with two crosses (the exhaust) on the opposite side. 3 x 1 x two lines can be added ...
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  • 295
3 votes
1 answer
163 views

Thieves for questioning

The police got three thieves when they tried to rob a bank. But the officer wants to give them a chance to get free, so he asks them who is the main brain behind the robbery. The thieves were puzzle ...
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  • 53
6 votes
7 answers
2k views

Probability that truth is spoken on Thursdays

A man speaks the truth on only two days a week. The days are the same for each week and they are in the TFT form (TFT = True False True. This means that the days on which he speaks the truth are ...
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6 votes
2 answers
331 views

How to prove Yin-Yang alternating 2 by 2 is not allowed

Yin-Yang is a puzzle where one needs to fill each cells with either black circle or white circle following these rules: Each color's circles must be connected to one another according to four-way ...
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  • 61
4 votes
3 answers
205 views

The Wrong Products

Rules: Place each number from 1 to 12 exactly once such that every row and column contains exactly two numbers. Clues outside the grid show the product of the two numbers in that row/column. However, ...
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  • 898
0 votes
0 answers
53 views

Can every Sudoku puzzle be solved without brute force? [duplicate]

So I wrote up an algorithm for generating Sudoku boards, and it generated the following board: I was trying to solve it on my own and got stuck, which prompted me to try putting it in this website. ...
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1 vote
10 answers
834 views

Two secret numbers [duplicate]

I have two identical pieces of paper. On each piece of paper I write down a number, either 1 or 2. I do not show or tell the numbers to anyone. My writing is always the same - if I write the same ...
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-2 votes
1 answer
198 views

Summa Cum Laude - Tile and Error

For any set X, {X} denotes the sum of its elements. "I divide {A}" means all items in that set are divisors of the sum of A's elements. Arrange the tiles so that four are in each set and the ...
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4 votes
1 answer
218 views

Puzzle 1.3 from Montague island mysteries

I'm on puzzle 1.3 "The Missing Painting" in the book Montague island mysteries I'm really struggling to understand the part in Taylor's instructions that says Keep in mind that a ...
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11 votes
5 answers
4k views

What is the next move on this minesweeper board?

Here is the board I found an online minesweeper solver which can deduce what the next move is, so I know what the next move is and that it is logically obtainable. But it doesn't offer much help in ...
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3 votes
2 answers
219 views

SNES Super Picross - Mario SP-I

Currently stuck on Super Picross and looking for a hint for the next logical deduction on Mario stage SP-I.
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  • 33
13 votes
1 answer
581 views

Mega Circles And Squares

Since recently Athin showed Circles And Squares, a genre which I invented and am very proud of, I thought "Hey, why not give another one!" But this time, I'm sharing one that I made for both ...
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2 votes
2 answers
220 views

Planar Investigator

Use logical deduction to place a different digit from 1 to 9 in each circle below so that 8 of the arrows form the primes 23, 31, 41, 53, 59, 79, 89, and 97. (We view an arrow starting at digit A and ...
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  • 14.5k
12 votes
2 answers
796 views

Circles and Squares - A Grid Puzzle

This relatively new grid puzzle genre is invented by Anonymus25. Rules of Circles and Squares: Shade some cells so that all shaded cells form one orthogonally connected area and each orthogonally ...
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  • 33.6k
3 votes
2 answers
212 views

What time is it? (High School Logic Question)

You need to find out what time it is. The logic question allegedly asked of middle school children in Russia. I think the question has more than one answer. So to clear my confusion, I will ask you to ...
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5 votes
2 answers
202 views

Ernie and the Disguised Donors

I was spending the morning helping Ernie dig up the potato patch when he got an emergency phone call from the Society for Absent-Minded Mathematics Professors – it appeared that they had “A bit of a ...
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  • 12.5k
2 votes
1 answer
220 views

Dark Ring III - The Combo City™

So uhm, it's a bit embarrassing, but I've spilled some coffee on my brand new Dark Ring III combo manual (Thank you all lots for the previous games!). I've been loving the game, I even bought it brand ...
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  • 4,702
1 vote
0 answers
151 views

A mysterious letter in the mail

The other day I got a letter in the mail.... It was a weird one, one that obviously boasts a puzzle. The Letter It states the following I like pigs, don't you? Won't you come and see the piggies with ...
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3 votes
1 answer
171 views

Dark Ring II - Scholar of the First Combo™

I need your help again people! After finishing Dark Ring I, thanks to you all, I went and bought the second game in the series. It's a lot more complicated, but I also learned a lot more from the ...
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  • 4,702
6 votes
2 answers
317 views

Dark Ring I - Prepare to Combo Edition™

My friend showed me a game recently, it's a little indie game called Dark Ring I, it's honestly pretty good and... I should get to the matter at hand. I'm reaching the final boss, and I tried looking ...
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  • 4,702
5 votes
1 answer
214 views

23 people wearing hats with a bell ringing [closed]

24 extremely intelligent people get invited to a really important party. Since it's really important after 9pm (the start time of the party) a guardian will guard the door to enter the party. All of ...
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8 votes
3 answers
6k views

"The Batman" puzzle: rataalada.com

I just saw the movie and went home to check whether the website www.rataalada.com actually exists or not, and surprisingly, it does! Judging by the news articles I found while searching, it's been ...
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  • 889
7 votes
1 answer
377 views

Identify someone as a truth-teller, liar or toggler with one yes/no question

You are visiting an island and need some information. The island has liars, truth-tellers, and togglers. Critically, togglers alternate truths and lies in their answers. When you meet someone, how can ...
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  • 79
3 votes
1 answer
272 views

A tough sudoku puzzle

Here is a tough sudoku puzzle from my blog
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-2 votes
1 answer
214 views

Easy Sudoku Puzzle

This is an easy sudoku puzzle (no. 90) from my blog.
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