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).
2,601
questions
-2
votes
0answers
62 views
Connect the Balls [duplicate]
Draw only 4 lines join all the 9 balls.
Hint-
Bonus Question-
Question Source
0
votes
0answers
82 views
How do I solve a 1 to 9 puzzle? [closed]
This is a 1 to 9 puzzle, where the digits 1-9, each once, must be used to fill the boxes. Each row, column, and diagonal must add up to the number shown. What technique can be used to solve this kind ...
18
votes
2answers
2k views
Making a 9 digit number divisible by 11
Alice and Bob play the following game, taking turns. Alice starts and writes a non-zero single
digit number at the blackboard.
At every turn, each player adds a single digit at the right of the ...
1
vote
1answer
400 views
Knight or Knave
On the island of knights and knaves (where knights always tell the truth and knaves lie), you meet two islanders named Penny and Quinru.
Penny: Both Quinru and I are knaves!
Who is a knight and who ...
3
votes
0answers
174 views
Her granddaughter is the only daughter of my brother
Pointing to a woman, Abhijit said, "Her granddaughter is the only daughter of my brother." How is the woman related to Abhijit?
Sister
Grandmother
Mother-in-law
Mother
Source of the ...
11
votes
0answers
217 views
Chess A Knight's Journey
You'll need to know about:
A game that has existed for over 1500 years
A game that doesn't exist
♞ → I → II → III → ...
Answer = Xxxxxxxxx
1
vote
1answer
81 views
Finding a lock combination [closed]
Here is a puzzle that I recently encountered:
You have a four digit lock with the following clues.
When you enter 1378, one digit is correct and well-placed.
When you enter 2834, nothing is correct.
...
17
votes
1answer
523 views
Slitherknot (Double Slitherlink)
This is a variation on the classic Slitherlink Puzzle. However, instead of creating one loop, you must create 2 separate loops.
The two loops can not share any edges, however they can cross or meet on ...
-6
votes
1answer
93 views
How is the boy related to the girl? [closed]
Pointing to a boy a girl said "He is the son of the daughter of the father of my only uncle. "How is the boy related to the girl?"
A standard yet simple technique will be highly ...
19
votes
1answer
1k views
Beans under the chessboard
Under every grid cell of a chessboard, I put either one bean or nothing.
Now if you choose a (grid) rectangular area on the chessboard, then I will tell you the parity of the number of beans under ...
10
votes
4answers
2k views
Who is the liar (Number of liars)?
There are 5 people. Each one can be lying or telling the truth, and they can't switch. Below, each person tells us how many liars exist in the group.
There are at least 3 liars.
There are at least 2 ...
2
votes
2answers
213 views
Four Mathematicians, Four Poker Hands and Four Clues
These four mathematician friends play poker every Saturday night. They always have a twist for the very last hand, just for fun.
This Saturday the twist was “Factorial Clues”. The rule for the last ...
8
votes
1answer
200 views
Gaps - Square Numbers
Rules of Gaps:
Fill some cells with stars, so that each row and column contains exactly two stars.
The stars cannot touch each other, not even diagonally.
Numbers outside the grid indicate the number ...
-1
votes
1answer
92 views
What replaces the question mark in the blood relation problem? [closed]
If A + B means A is the father of B If A × B means A is the sister of B
If A $ B means A is the wife of B If A % B means A is the mother of B
If A ÷ B means A is the son of B
What should come in place ...
-2
votes
1answer
137 views
A Blood Relation problem [closed]
In a family there are two married couples, two daughters, three sons and two brothers. Rohan is the son of Soni who is the daughter of Rajeev and wife of Lucky. Riya is the grand daughter of Rajeev. ...
1
vote
3answers
595 views
Blood relation problem - how is G related to S? [closed]
A is the son of P and brother in law of T, who is the sister of G. B is the husband of K. K has only two children, T is one of them. S is the mother of A and sister of W who is the husband of R. U is ...
14
votes
1answer
843 views
A walk after dark
This is a Palisade (or n-Cells) puzzle. The rules are:
Thicken some of the squares' sides so the thick borders outline cells. One such cell comprises just one square; one cell comprises precisely two ...
3
votes
2answers
162 views
On which date was Marina born?
The puzzle is as follows:
In 2012, which began on a Sunday, Marina was happy because her birthday was on a Saturday and she celebrated it with her friends. We know, Marina was born in a year where ...
8
votes
3answers
286 views
Toroidal Pipes Puzzle: T's and Bulbs Only
A continuation in the Pipes puzzle series.
Problem statement for math nerds: Let $G(N)$ denote the graph consisting of cardinally adjacently linked lattice points on an $N \times N$ toroidal grid. For ...
16
votes
1answer
1k views
When you stop at the top of a Ferris wheel
This is a Palisade (or Ten-Cells) puzzle. The rules are:
Thicken some of the squares' sides so the thick borders outline cells of ten squares apiece.
Any square with a number in it indicates how many ...
7
votes
3answers
400 views
Can you find and capture a shapeshifter?
A town was invaded by aliens, and some of its residents were kidnapped and replaced by shapeshifters. You're tasked with capturing one of the shapeshifters. Here's the setup:
There are 7 residents of ...
-5
votes
0answers
53 views
Mathematics based question [duplicate]
Vani meam has three Tatva books, one for chemistry, physics and biology. The chemistry book had 120 pages, the physics book has 10% more pages and the biology book has 10% fewer pages. In a class, she ...
13
votes
1answer
435 views
1
vote
0answers
50 views
Grids with tiles of two colors and connectors
Make a square grid with an even side.
Make a continuous trail which passes through all small squares; the trail ends where it started.
Where there is an angle you can put a red or a blue tile.
On ...
0
votes
1answer
68 views
How to solve the attached sudoku?
Please explain the logic. I am not trying to solve it using trial and error or using any software. I am just looking for the next step. This sudoku is from apple 'Sudoku King' app.
-4
votes
0answers
43 views
Rickey Rat puzzle [duplicate]
A powerful sorcerer has hired Rickey Rat as an intern. The wizard gives Rick the task of carrying water from a well to the garden. The path from the well to the garden is up a staircase with 1000 ...
2
votes
1answer
146 views
How could I solve the attached Sudoku?
Please explain the logic. I am not trying to solve it using trial and error or using any software. I am just looking for the next step. This sudoku is from apple 'Sudoku King' app.
1
vote
1answer
121 views
What is the greatest number of pencils that you cannot buy? [duplicate]
A shop sells pencils in boxes of 31 and 38. What’s the highest number of pencils a person cannot buy?
In general, if the shop is selling pencils in boxes of p and q, then what is the highest number ...
9
votes
1answer
958 views
My grandfather's coins
When my grandfather died, he left his fine collection of coins, not more than 2500 of them, to his children, a different number to each of them, and in decreasing amounts according to their ages.
To ...
12
votes
1answer
250 views
9x9 Sudoku Slitherlink Hybrid
I previously created a combined slitherlink and sukoku puzzle, but I was unsatisfied because the grid was smaller then a regular sudoku. So I made another, larger one.
Below is a 9 by 9 grid. This is ...
13
votes
3answers
2k views
What is the age of the old man?
In autumn of the year 2003 an old man was asked about his age.
He answered: "I was born on a Sunday morning in summer and I celebrated my seventh birthday
on a Sunday morning too!"
How old ...
9
votes
1answer
138 views
Sudoku: Episode 64 - Attack of the Clones
An 8x8 Sudoku where you technically only have to figure out 32 cells! Twice Half the cells, double the clues!
Penpa Link
Rules
Normal Sudoku rules apply. Values are 1-8. Boxes are the 4x2 regions
...
17
votes
2answers
570 views
Pipes Puzzle Uniqueness
In the puzzle game Pipes, a space-filling tree of pipes (which may have either one, two, or three neighboring connections each, but not four) is scrambled by a series of tile rotations, and the goal ...
1
vote
2answers
165 views
To Mock a Mockingbird: 4 brothers
On page 30 of Raymond Smullyan's book To Mock a Mockingbird, we are told that there are four brothers, indistinguishable in appearance, of which
Arthur is an accurate truth-teller,
Bernard is an ...
6
votes
1answer
202 views
A 3x3 grid with common factors
A $3 \times 3$ grid $G$ is filled with every number from the set $\{2,3,5,6,7,11,14,15,30\}$. Now a new $3 \times 3$ grid $H$ is formed, such that $H_{ij}$ is the number of neighbors of $G_{ij}$ that ...
11
votes
4answers
941 views
Deriving a 3x3 grid from another one
A $3 \times 3$ grid $G$ is filled with every number from $1$ to $9$. Now a new $3 \times 3$ grid $H$ is formed, such that $H_{ij}$ is the number of neighbors of $G_{ij}$ that are greater than $G_{ij}$....
-1
votes
1answer
160 views
How to create a logic grid given three categories?
How do they make the three category setup here? I do not understand how this works. A detailed answer to this is most welcome.
5
votes
2answers
655 views
Reasoning puzzle involving five friends and five departments
Five friends A, B, C, D, and E are working in 5 different departments M, N, O, P and Q and they earn different salaries i.e. 10,000, 15,000, 20,000, 25,000 and 30,000 and they all are of different ...
5
votes
1answer
128 views
Sudoku + Slitherlink
I like combinations of puzzles, so I decided to combine a Sudoku and a Slitherlink.
Below is a 6 by 6 grid. This is filled in with numbers based on the usual rules of sudoku. All of the numbers from 1 ...
-1
votes
1answer
118 views
Fillomino: Number Attack!
This is my first time making a Fillomino. Hope you enjoy!
Fillomino (taken from Nikoli):
Fill in all empty cells with numbers under the following rules.
Divide all of the board into blocks.
Fill ...
9
votes
1answer
487 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 ...
8
votes
5answers
1k views
Split 1 through 6 into a product of 24 and sum of 12
How many ways are there to split the numbers 1, 2, 3, 4, 5, and 6 into two groups, such that the product of the numbers in one group is 24 and the sum of the numbers in the other group is 12? An ...
21
votes
1answer
522 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 ...
3
votes
1answer
154 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 ...
-1
votes
1answer
124 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 ...
10
votes
3answers
892 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 ...
18
votes
1answer
379 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
108 views
15
votes
7answers
2k views
Flashlight and 8 batteries
A flashlight requires 2 AA-type batteries to operate. Both these batteries need to be charged for the flashlight to provide light.
We happen to have 8 batteries, but 4 of them are charged while the ...
3
votes
1answer
183 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 ...
