# 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).

2,892 questions
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-5 votes
1 answer
114 views

### Police Interrogation Puzzle [closed]

I have tried so hard to solve this puzzle. But I cannot get my head around it. I have attempted to eliminate the lies and I have come up with Dave as the criminal. But I do not know if it is the ...
-5 votes
0 answers
80 views

### 1,1,1,-17,? What's the next number and what's the pattern [closed]

1,1,1,-17,? What is the pattern and what number comes next
-3 votes
1 answer
95 views

### Square Sitting Arrangement [closed]

Eight people i.e., J, K, L, M, N, O, P and Q sit around a square-shaped table. Four people sit at the four corners of the table and face outside the table. Four people sit at the middle of the four ...
-4 votes
0 answers
51 views

### A balance scale logic puzzle [closed]

You have 16 coins, eight of which are heavy and of the same weight. The other eight are light and of the same weight. You do not know which coins are heavy or light. The coins look identical except ...
1 vote
4 answers
267 views

### Pipes and Tanks' Network

In the city XYZ, P is a water source from where water flows into the tanks – Q, R, S, T and U. The following diagram shows the network of the source and all the five tanks connected with pipes through ...
0 votes
1 answer
97 views

### Word Arrangement Machine Problem

Input: All Indians Are My Brothers And Sisters Step I: 23 32 12 38 65 17 81 Step II: 30 70 41 156 328 104 568 Step III: 568 328 156 104 ...
1 vote
1 answer
67 views

### My Fill-the-circles puzzles (Set #3)

In each puzzle, fill the circles with the numbers 1, 2, 3, ... n, where n is the number of circles in such a way that consecutive numbers are NOT in circles that are joined by a line.
4 votes
1 answer
105 views

### Find the 3 Item Amounts

Last week the store's receipt printer removed lines randomly from each item amount. A technician repaired the printer, but now it adds lines randomly to each item amount! The cashier told me that for ...
• 15k
0 votes
1 answer
81 views

### The Truth And Lies Today: Revisited

A man is only capable of telling the truth four hours a day, and they are either TTFTT or TFTTT (equiprobable). On the other twenty hours, he lies. All hours between 7pm and 6am are night, 7am and ...
• 157
1 vote
1 answer
136 views

### The Truth And Lies Today

Suppose a man only tells the truth three hours a day. It is the same every week and it is known that the pattern of the truth hours are TFTFT. (which means he may tell the truth at midnight and 2am ...
• 157
-1 votes
2 answers
101 views

### Which day of the week is today (Tuesday, Wednesday, Saturday or Sunday) if one of the statements is false?

Today is neither Sunday nor Wednesday. Tomorrow is not Sunday or Wednesday. Yesterday was not Friday. Monday was not the day before yesterday, neither was Sunday. Which day of the week is today (...
• 11
18 votes
3 answers
703 views

### Find the Two Item Amounts

I bought 2 items yesterday and the receipt was incorrect, so I asked the cashier about it. She told me that The receipt printer had been acting funny recently. The total is always correct, but some ...
• 15k
11 votes
2 answers
548 views

### The alien quantum-tunnelling hyperking labyrinth escape

Great title, right? Don't worry, I'll explain it. Here is the story. The inhabitants of planet Nuri have captured their arch-enemy, the hyperking of a neighboring planet (thus "alien"). ...
• 20.1k
4 votes
4 answers
184 views

### Constraint Satisfaction Problem: who killed Warren White?

Warren White was found shot dead one morning, police have then investigated who was behind the incident. There were 3 suspects who could be suspects in the incident. That afternoon, the 3 suspects ...
• 41
2 votes
1 answer
146 views

### Flipping through the faces of a cube?

Let's place a cube on a table and flip it around a bit. In fact, flip it according to the following instructions: Flip forward twice. Flip left twice. Flip backward twice. Flip right twice. Assuming ...
• 10.5k
5 votes
1 answer
166 views

### Sum Like It Simple

The three intersecting ellipses form seven curved regions. Place one tile from the seven candidates in each of these regions so that the tiles in any ellipse adhere to the corresponding rule. Show ...
• 1,238
-3 votes
1 answer
147 views

### Logical Connectives but 5 statements instead of 3 [closed]

Assume that each one of the numbered statements are individually true. Each of the two choices consists of a subset of these statements. Choose the subset as your answer where the statements therein ...
1 vote
2 answers
231 views

### Logical Connection Problems: which sets of statements are logically consistent? [closed]

Questions consist of a set of numbered statements. Assume that each one of these statements is individually true. Each of the five choices consists of a subset of these statements. Choose the subset ...
4 votes
1 answer
189 views

### Tribulation and Jubilation

Happy weekend puzzlers As ever from me a Venn-based game. The three circles represent as yet unknown categories - their intersection forms seven curved regions - and your job is to place the right ...
• 1,238
1 vote
2 answers
238 views

### 9x9 Sudoku Puzzle

This is a standard 9x9 sudoku puzzle from a book I hope to publish:
2 votes
2 answers
266 views

### I'm not a robot, I'm not a MONKEY

The city of Roboville has been invaded by robots, monkeys, and dancers, who will dance if the beat's funky. Some of the invaders can be two of them (e.g. both monkeys and robots) and some can be all ...
• 157
2 votes
1 answer
109 views

### My Fill-the-circles puzzles (Set #2)

In each puzzle, fill the circles with the numbers 1, 2, 3, ... n, where n is the number of circles in such a way that consecutive numbers are NOT in circles that are joined with a line. I designed all ...
6 votes
1 answer
138 views

### My Fill-the-circles puzzles (Set # 1)

In each puzzle, fill the circles with the numbers 1, 2, 3, ... n, where n is the number of circles in such a way that consecutive numbers are NOT in circles that are joined with a line.
0 votes
2 answers
324 views

### Is this Among Us logic puzzle possible?

In 11 Among Us players, some of them are crewmates, who always tell the truth, and imposters, who can either lie or tell the truth. Can you figure out who the imposters are? (There can be any number ...
• 157
1 vote
1 answer
134 views

### More of my Find-the-stars puzzles (Set #2)

Find-the-stars instructions: A Find-the-stars puzzle is played on a square grid that is initially empty except some squares contain arrows. The goal of the puzzle is to fill some empty squares with ...
9 votes
2 answers
338 views

### Three of my Find-the-stars puzzles

Find-the-stars instructions: A Find-the-stars puzzle is played on a square grid that is initially empty except some squares contain arrows. The goal of the puzzle is to fill some empty squares with ...
5 votes
1 answer
170 views

### Sobot or fauxbot?

Through the bustling hallway, you followed your speed-walking, speed-talking brother, who was hoping to submit an article about the upcoming demonstration to his beloved Logic and Philately Semi-...
• 701
1 vote
1 answer
142 views

### Honeycomb puzzle with hexagons [closed]

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 ...
8 votes
2 answers
678 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 ...
• 155
-2 votes
1 answer
119 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?
3 votes
1 answer
162 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 ...
• 1,238
0 votes
1 answer
100 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 ...
• 325
2 votes
1 answer
78 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.
• 5,298
5 votes
1 answer
154 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 ...
• 5,298
-1 votes
2 answers
144 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 ...
• 109
11 votes
1 answer
233 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 ...
• 701
4 votes
3 answers
260 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 ...
• 28.8k
10 votes
1 answer
757 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 ...
• 289
6 votes
1 answer
301 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 ...
• 1,238
4 votes
2 answers
511 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 ...
• 157
-1 votes
1 answer
159 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 ...
• 619
4 votes
2 answers
173 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:...
• 908
25 votes
9 answers
3k 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 ...
• 4,883
8 votes
3 answers
958 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 ...
• 5,501
2 votes
1 answer
202 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 ...
• 15k
1 vote
0 answers
67 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 ...
• 125
6 votes
1 answer
246 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 ...
• 701
5 votes
2 answers
605 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, ...
• 3,460
3 votes
1 answer
160 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 ...
• 1,465
5 votes
1 answer
580 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 ...
• 5,501