We’re rewarding the question askers & reputations are being recalculated! Read more.

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).

Filter by
Sorted by
Tagged with
1
vote
2answers
414 views

How much does the bag actually weigh?

A grocer has a set of two-pan balance scales for weighing food. A customer weighs a bag of sugar on one of the pans, which registers at 45 pounds. Suspicious, she swaps the bag to the second pan of ...
-5
votes
2answers
376 views

A few (very) easy puzzles [closed]

There are 7 sisters in a house. First one is reading a book, second is cooking, third is playing chess, fourth is solving sudoku, fifth is doing the laundry, sixth is watering the flowers. Question: ...
7
votes
1answer
1k views

Password Out of Date

Bob works at a high security institution. One day Bob tried to log into his computer and his password was denied. Then remembered that, for security reasons, the passwords were reset every month. So ...
9
votes
2answers
864 views

Color-Coded Bridges

Use the given clues to solve the puzzle below. Note: an image editing tool is recommended.
46
votes
10answers
16k 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 ...
3
votes
1answer
372 views

Finding a murderer from statements from suspects

Officer X was entrusted with the duty of investigating a murder. The dead body was found in the living room. Preliminary investigation suggested that four of the six suspects were liars (at least one ...
6
votes
2answers
440 views

The 169 members of the Dinner Club

The Dinner club has 169 members, and professor Erasmus is one of them. Every evening, four of the members meet and have dinner together in a fancy restaurant. Professor Erasmus claims that today is a ...
8
votes
2answers
744 views

In the space station

There is a space station which has several chambers and each chamber is connected with a tube. Five mathematicians A, B, C, D, and E were gathered in a lounge of the space station. Suddenly, E ...
-2
votes
2answers
199 views

Shifting the stack as it is

There are $3$ saucers. And there are $5$ disks, say A,B,C,D,E, having respective areas $1,2,3,4,5$. That is, E is the largest disk and A is the smallest one. They are placed in the order E,D,C,B,A in ...
6
votes
3answers
507 views

Paying for drinks with Mexican and Texan dollars

The story is told that when the Republic of Texas was feuding with Mexico, there was a law passed by Texas to the effect that a Mexican silver dollar was worth only 50 cents in Texas; whereupon Mexico ...
-4
votes
1answer
2k views

How can the man get across the river with the two animals and the cabbage? [duplicate]

A man has a wolf, a goat, and a cabbage. He must cross a river with the two animals and the cabbage. There is a small rowing boat, in which he can take only one thing with him at a time. If, however, ...
-2
votes
2answers
509 views

Binary manipulation game

I made a (for now, 2 player) game once that deals with manipulating binary numbers on a single list. Here are the rules. Rules For now, take $n=5$. If possible, provide a solution for generalized $n$...
4
votes
2answers
923 views

Island inhabitants: Who lies and who tells the truth? [duplicate]

On some island, the population is split into native people and into outlanders. There are more natives than outlanders. Someone with extreme logical and mathematical thinking wants to know who are ...
3
votes
1answer
261 views

Colorful grid: how to place tiles to get the most points?

We have a 5x5 grid, on which we can place colored tiles, one by one. The goal is to create a grid with the highest amount of points. The tile colors are: Blue (1 pt) Red (2 pt) Green (3 pt) Yellow ...
-3
votes
2answers
233 views

Are rotton apples edible? [closed]

Choose the conclusion that validly follows from the argument below. Some apples are edible. All edible food are not rotten. Therefore A. All apples are not rotten. B. Some apples are rotten. C. ...
2
votes
3answers
289 views

Consecutive ranks?

Tom, Paul and Joe have just learnt the ranks that they reached in a competition. None of them knows the ranks of the other two, but they all know that Tom and Paul ended up in consecutive positions. ...
7
votes
2answers
454 views

Link the hints to solve this one, starting with Michael Jackson

This is a linking puzzle, where you get 8 hints, and 7 links between them. Michael Jackson made a song for this film. 1.-2. The link between the animal of clue 1 and the fictional person of clue 2 ...
6
votes
4answers
279 views

At least $N$ false statements

Let $N$ and $M$ be two integers with $M\ge N\ge2$. There is a list of altogether $M$ statements that is divided into three parts: the first part consists only of the first statement; the second part ...
6
votes
2answers
502 views

How many knights

In a room are 13 men, who are either Knights (truth tellers) or Knaves (lie tellers). the first man looks around and says "The number of knights in this room is no greater than one" the second man ...
21
votes
3answers
3k views

Winning an unfair game

I came across the following interesting problem today: A game consists of a sequence of plays; on each play either you or your opponent scores a point, you with probability $p < \frac{1}{2}$, he ...
10
votes
3answers
573 views

Arnie and Barney: When is Barney's birthday?

The following twelve statements were made on a certain day X during the last 100 years. At least seven of these statements were true on day X: Exactly one month from now it will be Thanksgiving. ...
11
votes
2answers
9k views

Divide a rectangle with a rectangular hole into two equal parts

Consider any large rectangle from which a smaller rectangular portion has been removed. The removed rectangular portion may have any orientation i.e. the remaining figure is not necessarily symmetric ...
14
votes
12answers
3k views

Up to your head in trouble

You've gotten in trouble with a Mob Boss, and as punishment have been brought to a sandy beach. You're ordered by him at gunpoint to bury yourself in the sand up to your neck. He specifies a spot ...
8
votes
1answer
869 views

Number of tries to guess M-1 letters from M-letters-code

There are $N$ letters in an alphabet. There is a combination lock, the code to it consists from $M$ different letters. You can input $M$ letters combination and try to open the lock. (But you can't ...
5
votes
3answers
806 views

8 chess players in a round robin tournament

Eight people played chess in a round robin tournament. No match ended in a tie and both A and B won the first place. Since C and D were rivals, C beat all players who beat D and D beat all players ...
9
votes
3answers
1k views

n - archers and many arrows

Suppose there are n archers in a standoff and want to kill each other until there is just one archer remaining. However everyone's chance of hitting (and thus killing) another archer is not fair. ...
6
votes
2answers
790 views

Exercise with a piece of code and x[2][5]

I was given this exercise to solve. It's beyond me, but important for me to solve this. The following piece of code is all the context I was given. ...
7
votes
2answers
2k views

A list of 100 statements

I was working my way through some puzzles in Discrete Maths by Rosen, when I came across the following question: The $n^{th}$ statement in a list of 100 statements is : "Exactly $n$ of the ...
0
votes
3answers
2k views

Puzzle : Who is Corrupt in the Senate?

I was working my way through some puzzles in Discrete Maths by Rosen, when I came across the following question: Freedonia has fifty senators. Each senator is either honest or corrupt. ...
6
votes
1answer
4k views

Are there 'Hexanum' puzzles that require advanced methods to solve? [closed]

The puzzle below features each week in a TV guide. It's called "Number Workout" there but I've done a bit of research and it seems to be called "Hexanum" elsewhere. It bears some resemblance to Sudoku,...
8
votes
2answers
624 views

Pathfinding with disappearing platforms - is it solvable?

This is a puzzle but might not have a solution. So "is it possible?" is a proper question. The puzzle idea was inspired by the question logic problem/puzzle solving, and if the puzzle here turns ...
5
votes
2answers
551 views

Balancing all but one weight

You have an odd number of tokens whose weights are known whole numbers, and they don't all have the same weight. Show that there's a token you can remove so that the remaining tokens can't be split ...
11
votes
7answers
2k views

Using a balance scale the minimum number of times, find the median weight person

There are 15 person with different weights. What is the least number of tries required to find the middle (median) weight person? How? The only tools you have is your brain and a balance scale with ...
8
votes
2answers
624 views

Middle weight puzzle

There are 100 white and 101 black balls. All the balls have different weights. Balls of the same colour look the same. White balls are numbered from lighter to heavier (from 1 to 100). The same is ...
-2
votes
1answer
713 views

Find the Different Sugar Cubes [duplicate]

There are 10 Boxes, each contains 1000 sugar cubes. The sugar cubes in 9 of the boxes are 10 grams each and the other box has 9 gram cubes. There is a digital scale that you can use it ONCE. (i.e. ...
3
votes
1answer
536 views

200 Discs - weighing problem

You are an intrepid explorer who has been caught in a trap by a primitive tribe. They lock you in a room with no exit but one door. The door has a pressure sensitive release - incorrect pressure ($>...
4
votes
1answer
579 views

Which one is the lightest marble?

There are 8 marbles that one of them is lighter than the others, and all other seven marbles have the same weight. There is a balance scale that you can use it twice or once. Is there any way to find ...
3
votes
2answers
396 views

How many magazines?

You would like to sort some monthly magazines in different categories. Disregarding the title of magazines, there are 4 different categories if you arrange magazines by publishing year and month. ...
9
votes
1answer
610 views

Recover the Ripped Quote

Bruce found a nice quote on the web, then wrote it in on a square piece of paper and left it somewhere in his room. The quote had exactly 64 characters excluding spaces. He has written the characters ...
4
votes
3answers
1k views

At the Parking Lot

Alice and Bob started working part-time parking lot attendants. Bob was managing a car when Alice arrived late on the first day at work. A: I'm sorry for being late. How many cars have come in? B: I ...
3
votes
0answers
114 views

Magical election of novices in a monastery [duplicate]

In a monastery, there is a special rite to elect new novices. All candidates (we're talking of a huge number, so let's assume an infinite amount) gather together in one hall that gets locked, so that ...
8
votes
4answers
5k views

What is the sitting arrangement ?(double row question)

Question: Eight people are sitting in two parallel rows containing four people each, in such a way that there is a equal distance between and adjacent persons. In row 1 , A,B,C,D are seated and all ...
8
votes
1answer
2k views

100 Marbles Puzzle

Here's a puzzle I heard some time ago, but I never heard the asker's solution. It took me ages to think up a satisfactory solution, but I'm wondering if there are any others you can think of? 100 ...
1
vote
2answers
210 views

need help with a math equation puzzle [closed]

I'm trying to create a math equasion puzzle using the numbers 3, 7, 20 and 40. I want to end with an answer of either 7 or 40. Is there any way this can be done? Thanks for the help
14
votes
1answer
1k views

How to ensure your logic puzzle has no loopholes?

Alright, say you've made this logic based puzzle, but when you post it, people find tons of loop holes, that obviously wasn't what you want! You didn't tag it with lateral-thinking or brainteaser! It'...
18
votes
8answers
2k views

When should you rest?

You are in an airport and are worried about missing your flight. So you start to run the long distance to the flight gate at a steady speed of 10km/h (you have bags and are not very fit). ...
3
votes
2answers
2k views

whats the Missing Number?

In this grid of numbers, what is the missing number (in place of the question mark)? $$\begin{array}{|c|c|}\hline2&7\\\hline8&9\\\hline\end{array} \begin{array}{|c|c|}\hline0&3\\\hline5&...
4
votes
2answers
4k views

Puzzle : O' Barber , Who Art Thou?

I was working my way through some puzzles , when I came across the following question: An ancient Sicilian legend says that the barber in a remote town who can be reached only by traveling a ...
0
votes
0answers
104 views

A soft puzzle about a deaf ,dumb and a blind person [duplicate]

A deaf person stole a blind person's hen and a dumb person witnessed it.How can the dumb person convey this to the blind person?
18
votes
3answers
3k views

Binary Minesweeper

This Puzzle is a form of the classical MS Minesweeper which keeps popping into my head. In Minesweeper, a 2D grid is filled with mines and numbers whereas each number represents how many of its 8 ...