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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9
votes
1answer
490 views

Plants vs Zombies!

Several plants and zombies (no more than 20 creatures in total) came to the party “Plants VS Zombies”, and it turned out that all the creatures are of different heights. When a plant speaks to a lower ...
16
votes
4answers
3k views

How many smurfs are there?

Papa Smurf gathered some berries from the forest to the village and smurfs ate all those berries: The smurf who ate the most actually ate one-fourth of the berries eaten by the rest of the smurfs. ...
6
votes
2answers
1k views

A new puzzle - Sudoku X V

If someone is able to find the solution... I found 2,3,8 on line 5, column 3-4-5, but after that I am blocked, it looks too difficult for me.
10
votes
3answers
900 views

Calculation Sudoku

Here is a new quiz from my daily quiz calendar. I'm trying to find a way to solve it. The numbers 1-6 should be filled in. And like a sudoku, each row and each column should contain each number ...
3
votes
1answer
162 views

9 people sitting at a round table

I am unable to figure out how to solve this question @Joffan has given an answer but he hasn't mentioned much regarding his approach. I requested him but he still didn't give a clear answer. This is ...
21
votes
1answer
531 views

Slitherlink: Around the W0rld

Rules of Slitherlink: Connect adjacent dots with vertical or horizontal lines to make a single loop. The numbers indicate how many lines surround it, while empty cells may be surrounded by any number ...
-1
votes
1answer
126 views

Skyscrapers 7x7 How to get next Skyscraper on field

I have the following Skyscrapers puzzle: C3 C1 C2 C3 C4 C4 C2 C2 V3 C5 C4 V1 C1 C3 C4 C2 V5 C3 C3 V7 C3 C3 V4 V2 C2 C1 V2 C2 C1 C3 C4 C2 C2 C2 C2 C -> Clues how many ...
9
votes
2answers
627 views

I'm Bad at Naming Things, so Just Try to Solve this Patterned Masyu Puzzle!

The original Masyu rules apply. Make a single loop with lines passing through the centers of cells, horizontally or vertically. The loop never crosses itself, branches off, or goes through the same ...
4
votes
1answer
740 views

Beating at Eating, a logic-grid puzzle for literal logicians

Name Surname Dessert 1 Agatha Greed cream puffs 2 Bugsy Forager trifle 3 Delilah Eatalot cheesecake 4 Chuck Hunk ice cream Four friends held a competition to see who could eat the greatest amount ...
14
votes
2answers
664 views

Distance Puzzle

The rules are: 1. Draw two circles (O) in the empty cells in every row and column. 2. The numbers in the black cells indicate the space between the 2 circles in the black cells' row or column, in ...
18
votes
1answer
390 views

A constrained, but concerning, celestial confrontation

An entry in Fortnightly Topic Challenge #52: Polyominoes. This puzzle is a hybrid between Pentominous and Star Battle. Your job is to divide the grid below into pentominoes according to the rules of ...
1
vote
1answer
113 views

Next Move on this Sudoku Classic

What would be the next move? Link to this sudoku
3
votes
2answers
126 views

Five possible liars - any way to solve with a grid-based method?

The situation is as follows: At a semiconductor laboratory in Hsinchu a security guard caught five technicians accessing a high level security area reserved for the most trusted scientists working in ...
10
votes
5answers
983 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 ...
46
votes
10answers
18k views

Puzzle: Who hacked the computer?

I was working my way through some Knight and Knave Puzzles in Discrete Maths by Rosen, when I came across the following question: Four friends have been identified as suspects for an unauthorized ...
71
votes
28answers
18k views

You have one question to tell whether the number I'm thinking of is 1, 2, or 3

This is an interesting puzzle which was passed to me by a friend some time ago. I do know the answer, but will refrain from self-answering on this to see where it goes. I'm thinking of a number: 1, 2,...
45
votes
4answers
8k views

The coolest checkerboard magic trick

In the small town of Terni (Italy), there's a couple of young friends named Marco and Leonardo, who like to perform magic tricks to a restricted audience of common friends and relatives. They like to ...
2
votes
1answer
424 views

Baggage Mishap Logic Grid

This is a puzzle from Braingle: Savannah got distracted when her shuttle arrived at Earth Central Airport. Now she's at Lost & Found with four other travelers all waiting to retrieve one lost ...
3
votes
1answer
190 views

3 weird images from a friend

I got sent this from a year ago, and I am still thinking what was the secret number that they hid a secret from, so here are the pictures. The first one was a car, and a random equation. The next one ...
-2
votes
2answers
287 views

How old is Brenda?

Five friends (Adele, Brenda, Carol, Dana and Emily) were born peculiarly in consecutive years. It is known from their diaries that: Carol was born 2 years before Dana and is not the oldest of them all....
4
votes
3answers
792 views

Why is the next Sudoku step a 6?

I used a step-by-step Sudoku solver for a puzzle in which I was stuck. However I don't understand how the next number (6) was found. Sudoku puzzle where I was stuck: Sudoku puzzle solved by one step ...
1
vote
1answer
91 views

4-DominoBrane #002 “81”

Here is another domino puzzle. This is considerably easier than puzzle set earlier this week, and definitely doesn’t need bifurcation. This uses 4-Dominoes (all the normal dominoes, minus any with a 5 ...
1
vote
1answer
122 views

4-DominoBrane Exclusive

Here is a smaller puzzle from the set of domino puzzles, I call DominoBrane. This uses 4-Dominoes (all the normal dominoes, minus any with a 5 or a 6). Each domino ...
14
votes
1answer
295 views

Tapa on a Penrose Tiling

An entry in Fortnightly Topic Challenge #51: Non-rectangular grids. This is a standard Tapa puzzle, on a non-standard Tapa grid...the "grid" is a Penrose tiling! Since the grid is not ...
3
votes
1answer
235 views

Slitherlink: The Couple of Question Marks

This is my first slitherlink puzzle. I made it myself. Feedback is appreciated! (I hope this one has a unique solution, unlike my other past puzzles, wink). Rules of Slitherlink (taken from Nikoli): ...
15
votes
1answer
317 views

Haisu: Schezo's Birthday

Rules of Haisu: Draw a path from S to G passing through all white cells exactly once by connecting the centres of adjacent cells. When the path passes over a number N, it is on its N-th entry to the ...
2
votes
1answer
265 views

Arrange candies without repeating pattern

The following puzzle had been posted before but I couldn't understand the only answer that was given there, which was by @neodne . So, I created this post asking someone to explain neodne's answer to ...
7
votes
3answers
620 views

One truthteller, one liar, and two randoms - least questions to identify?

I have landed on a new planet and there are 4 people there. One of them is a truth teller and they always speak the truth. The other is a liar and they always lie. The other 2 are random and they ...
3
votes
1answer
161 views

Swapping eggs puzzle

You can try this with pencil and paper, or make it a physical puzzle you can try out with your kids if you have one of those large 3x6 egg cartons laying around. Imagine you have 3 rows of 6 spots. ...
10
votes
1answer
298 views

The Nurikabe of Peace

Today is the 75th anniversary of Sir Winston Churchill's speech "The Sinews of Peace" which introduced to the world the phrase "The Iron Curtain". This puzzle is inspired by that ...
4
votes
2answers
485 views

Grid of numbers and dashes, X-Akseli and Y-Ehe?

I have been given this puzzle by my friend (who is a qualified military cryptographer). I am completely stuck as for what to do. They gave me this hint: "Don't take it so literal, think in all ...
19
votes
1answer
431 views

Escape from Sudoku!

An entry in Fortnightly Topic Challenge #50: Escape Rooms I hesitated to enter this in the Escape Room FTC, but I definitely was inspired by the challenge to create this puzzle, and it is, in some ...
8
votes
2answers
222 views

Double sudoku - two-digit numbers, the 1s and 10s places both form Sudokus [closed]

Using distinct 2-digit numbers from 11-99 that have no zeros, fill in the grid so that the tens digits form a Sudoku and the units digits form a (different) Sudoku. There might be a mathematical way ...
7
votes
4answers
773 views

Sorting 6 boxes by selecting 3 boxes each time

There are 6 boxes, each containing a distinct number. You can select 3 boxes and the Oracle will tell you which box has the smallest number and which has the largest number of the three selected boxes....
1
vote
5answers
200 views

Another (simple) self-referential aptitude test

Nine months ago I started my journey on Puzzling in a rough way with this question. I honesty hope this time I won't generate so extended discussion...! I love self-referential questions, puzzles or ...
14
votes
1answer
559 views

Shingoki: An Exploration of Unicode

An entry in Fortnightly Topic Challenge #42: Wordless Connecting Walls-- wait, what? This is a Shingoki puzzle. The rules (paraphrased from puzzle-shingoki.com) are as follows: The aim is to form a ...
13
votes
9answers
4k views

How to get 32 by using +1 , +1 , ×3 , ×3 , ÷2 , ÷2, ^2, ^2?

How to get 32 by using +1,+1,×3,×3,÷2,÷2,^2,^2? (The last two operators are 'squaring'.)
1
vote
4answers
156 views

I need some help with this 15x15 nonogram

I have been working on this nonogram for some time and can't seen to figure out what to do next... This is the link: https://nonograms-katana.com/play/#game
11
votes
6answers
13k views

1 Fake Coin among N Amount of coins

You are given $N$ coins which consists of only $1$ fake coin. You also have a sensitive old-fashioned Pan Balance Scale. You are asked to find the fake coin in totally 5 times weighing on the Pan ...
5
votes
1answer
233 views

How to get the least possible sum in a closed loop set of squares?

The puzzle is as follows: The figure from below represents a set of 12 squares joined forming a closed loop. By using only the numbers from 1 to 12 fill in the blanks. The condition is that, without ...
8
votes
1answer
224 views

Nurikabe: The Terrible Tower of Threes!

This puzzle is a quick and fun little Nurikabe that is very tall, because I am not. It's not particularly tough, but if you need a nice relaxing grid-deduction puzzle to calm your brain today, this ...
9
votes
1answer
394 views

Trivia… sudoku

An entry in Fortnightly Topic Challenge #49: Pub Quiz Camouflage Please do not search the answers online (hence the no-computers tag), otherwise it would be too simple to solve this puzzle. I tried ...
-1
votes
2answers
114 views

How to find the least number of extractions to make the word QATAR?

The riddle is as follows: A local library has lended its catalog card cabinet so it can be used in a raffle. The raffle prize is a luxurious travel to the Middle East for vacations to an employee ...
3
votes
2answers
497 views

Matches to move in order to get right roman numeral over fifty

The riddle is as follows: The figure from below represents a set of roman numerals wrote in such a way that the sum is not correct. The numbers are arranged as: 50+12=51 How many matches minimum ...
9
votes
7answers
502 views

3 travelers and 9 diamonds

There are three travelers. They are inside a cave. Deep down in this cave, there are three doors, each door containing at least one diamond, and there are a total of 9 diamonds. Each traveler picks a ...
-2
votes
2answers
113 views

How many have to enter the building so their birthday matches?

The riddle is as follows: Looking at his watch a doorman from an hotel in New York notices that 280 people are inside. Suddenly he begins to ponder the following. How many people should have to come ...
3
votes
1answer
142 views

Seven letters riddle

Hoping it is a never-seen riddle, here is the problem. We have seven letters A,B,C,D,E,F,G. Each letter is associated with a unique number between 1 and 10. We know the following: D is 3 units ...
10
votes
3answers
430 views

We have captured 5 spies. Their names are A, B, C, D, and E

This is a variant of the puzzle here. We have captured 5 spies belonging to a secret organization. Their identities are unknown; we only know them by their codenames A, B, C, D, and E. After thorough ...
1
vote
1answer
233 views

Husbands and Wives around a Circular Table

Transcription from this image. Some of the list formatting has been slightly altered to make it play nicer with Markdown. Eight persons, A through H, comprising four married couples, sit around a ...
1
vote
1answer
124 views

Number crossword puzzle

I'm trying to solve the following quiz from my daily quiz calendar (I have it in paper so I cannot give a link). It's like a crossword puzzle but with numbers. The empty cells should be filled with ...

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