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).

7
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2answers
1k views

An Accountant Seeks the Help of a Mathematician

The accountant complaints to the mathematician: “I lent money to five other faculty members and still haven’t been paid back. You are one of them; the other four owe me 12 dollars altogether, but ...
16
votes
3answers
2k views

Four buttons on a table

I was asked lately (in an interview) to solve this puzzle, which is similar to the 4 cups on table puzzle. In a certain room there is a rotating round table, with 4 symmetrically located ...
0
votes
0answers
57 views

Electric switch [duplicate]

There are 3 switches in a room and a bulb in another room far away. One of the switches turns the bulb on. How can you find the switch which turns the bulb on by going to the room only once?
7
votes
1answer
566 views

Who attempted to betray the Boston King?

The Castle of Weshire recently declared war on the Castle of Boston. The two armies soon met, the Boston King and Weshire King giving out orders from behind their lines of soldiers, surround by their ...
1
vote
2answers
5k views

Missing is what in picture

Source: http://gpuzzles.com/mind-teasers/pattern-series-picture-puzzle/?source=stack What is missing in the picture?
4
votes
2answers
237 views

What's the problem with the prisoner to be hanged logic puzzle

A criminal is imprisoned on Monday, and told "you will have been hanged by the weekend, but you won't know which day we'll hang you." If it gets to Thursday midnight and he's not been hanged yet, he ...
2
votes
1answer
1k views

Possible answer to the Heaven Hell Door riddle

There is a fairly common riddle You're standing between the door to heaven and the door to hell. A guard stands by each door. One guard always tells the truth, and the other always lies. You don't ...
8
votes
2answers
319 views

Poisoned Glasses on a Platter

Three identical, mute triplets, $F$, $S$, and $T$, each of whom is a perfect logician, have been kidnapped. Their captor begins by instructing them that in a room that they will shortly enter, are six ...
-3
votes
3answers
243 views

Only one option is correct [closed]

$a \in \mathbb{C}$ Which is the correct option: 1) $a = 1$ 2) $a = 42$ 3) $a = i =\sqrt{-1}$ 4) $0^a \in \mathbb{C}$ 5) $a^3 = 1$ Hint 1: Hint 2:
2
votes
1answer
174 views

Binary Bob's Programming Language Puzzle

Binary Bob Needs Your Assistance Bob's Dilemma Binary Bob is considering going back to school to learn computer programming, however, Bob has been given some jumbled course information. Bob needs ...
66
votes
26answers
14k 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,...
3
votes
1answer
188 views

$n$ buttons on a table

A generalization of Four buttons on a table: In a certain room there is a rotating round table, with 4 symmetrically located indistinguishable buttons. Each button can be either ”on” or ”off”, ...
3
votes
3answers
338 views

Word Cipher with seemingly random numbers

I came across this interesting puzzle and have failed to crack it for more than three days. Can you solve it? m.imdb.com/title/tt2039338/ L=9, 20, [2x5], 6, 17, 13 W=38 The only tips I ...
2
votes
1answer
171 views

Tokyo Metro puzzle special #2: The tour of the Metro

This is a simpler puzzle: How many stations do you have to pass by to pass by every station of the Metro? map Please either 1) explain your solution or 2) make an image of the route. Once consensus ...
2
votes
1answer
194 views

Pattern recognition puzzle, …$5$ , M , $6,5040,$ … ; then M=?

The following pattern puzzle problem was given to me by one of my friend: $$\color{red}{5}$$ $$\color{blue}{24 \quad \quad \quad \text{M}}$$ $$\color{red}{4 \quad \quad \quad \quad \quad 6}$$ $...
0
votes
2answers
166 views

Pattern recognition problem: if $2 \star 8 \star 8 = 161642\dots$ then M=?

The following sequence was given to me by one of my friend: $$\color{red}{2 \star 8 \star 8 = 161642}$$ $$\color{blue}{4 \star 9 \star 7 = 362843}$$ $$\color{red}{7 \star 5 \star 9 = 356344}$$ ...
2
votes
2answers
134 views

Tokyo Metro puzzle special: Oops, the lines are coming down

Here is my first Special Edition puzzle, and it is a little harder. The map is also available as a PDF. So you, being a Tokyo straphanger, was in between Hikawadai (Y05 F05) and Kotake-mukaihara (...
8
votes
3answers
1k views

A first choice die

You and your friend have met to play a game of dice. This is a very simple game where both players roll a die at the same time, and the player with the lower score pays a coin to the other player. In ...
4
votes
1answer
140 views

Minesweeper challenge #5

Coming back to another Minesweeper challenge... I've run into another "unsolvable corner" (corner of a puzzle where there isn't enough information to be 100% certain that any particular square that ...
2
votes
2answers
245 views

Unlock an answering machine using minimum number of digits

You know of answering machines with a remote inquiry facility, where you can call the answering machine and enter a four digit passcode into your telephone keypad, so you can listen to your messages ...
14
votes
3answers
797 views

Treasure Hunt Riddle

John and Peter participate in a treasure hunting competition. The organizer places a gold medal in one of the lockers. The locker rack contains 49 lockers, each of which has a name indicating its row ...
7
votes
3answers
469 views

Guess simultaneously, color of your hat, no passing allowed

1000 logicians standing in a circle are blindfolded and a hat of either black or white color is placed on each person's head. The blindfolds are then removed and each person can now see everybody's ...
8
votes
2answers
372 views

Houses and Telephone #s

There are 16 houses consecutively numbered 1-16. All houses have 7-digit telephone numbers, numbered consecutively, in the same order. For example, if house #3's phone number is 1111111, house #4 will ...
4
votes
1answer
206 views

systematic number removal [duplicate]

The whole, natural numbers 1 through 50 are written on a board. The following operation is performed 49 times: select any two of the numbers on the board and write the absolute value of their ...
4
votes
1answer
413 views

Analyzing Single-Elimination Tournaments

I know there are many questions/answers about single elimination tournaments out there, but I wanted to approach this question in a more holistic way. For a single-elimination tournament with N ...
7
votes
2answers
248 views

Integers in Cells puzzle (sudoko-like)

All the whole numbers 1−9 are placed in the 9 triangular cells. A negative sign is placed in front of some numbers. The letters A−F are products of 3 or 5 of the numbers. Find all possible ...
24
votes
5answers
4k views

The No-Straight Maze

Consider the following maze. You can walk on the black lines, and your aim is to go from the green at the maze's bottom to the red on the left side. However, each time you reach an intersection of ...
9
votes
2answers
6k views

Crack the 5 digits code

I created this "crack the code" puzzle. I hope the members here like it.
34
votes
16answers
5k views

XKCD inspired logic puzzle

I came up with a logic puzzle inspired by this xkcd comic. I don't yet have an answer, and I am wondering if anyone can come up with one. You are in a room with three doors. Two of the doors lead ...
4
votes
4answers
2k views

Generate the number for Sunday by finding the pattern

I found this puzzle on another site so I put it here to share with you. I will give link for the pattern logic of given puzzle. Answer: Click here
6
votes
2answers
330 views

Find the Rogue with AOE

You are playing World of Warcraft which is well known an old MMORPG game. You are in arena where you play against another player. You are a mage and the opponent is a rogue which can hide while moving ...
9
votes
2answers
326 views

A weird number system (I made it myself)

So, I'm an eccentric mathematician. You can see this with my number system. I'm pulling a sneaky on you, and you'll have to tell me what everything means. I'm not telling you a thing: figure it for ...
7
votes
2answers
930 views

Hat puzzle - 7 prisoners

There are 7 prisoners buried up to their necks in sand. 6 are on one side of a wall, all facing the wall. They are lined up such that the furthest from the wall can see the 5 prisoners closest to the ...
0
votes
1answer
146 views

How many trees and birds are there? [closed]

There are 'X' number of Trees and 'Y' number Birds. If 1 bird sits on each tree then 1 BIRD will be left. If 2 birds sits on each tree then 1 TREE will be left. What is number of trees(X) and ...
9
votes
3answers
541 views

The heritage of a numismatic

The old rich Jeremiah has two sons, Timothy and Joseph. One day, Jeremiah decides to discuss about his heritage with his sons... JEREMIAH: Dear sons, I'm very old and exhausted, so I want to ...
5
votes
1answer
265 views

Stuck in 6x6 skyscraper puzzle

I don't know how to continue, can anyone tell me which next number am I able to add? Here is the puzzle (there are clues at edges), and below are possibilities. Feel free to tell me if I made mistake, ...
11
votes
3answers
3k views

Where did they find Gold?

A lesson in US Colonial history. ( A stretched version) After the thirteen colonies declared independence they needed resources badly. So the enterprising brave pioneers of those times set out to ...
4
votes
4answers
265 views

Weighing Counterfeit coins

There are $n=4$ coins and we know exactly $2$ of them are counterfeit. In $2$ weighings, how can we find which of the four coins are the counterfeit ones? Assumptions: the counterfeit coins look ...
0
votes
1answer
206 views

Puzzle on arrangement of blocks [closed]

"The post has been edited. I am adding the answer in a few moment(references to which you are going to find in the doubts section)" Doubt: I have found out the 'initial' arrangement as given ...
5
votes
6answers
382 views

A Gambling Problem You Would Love To Have

Let's play a quick gambling game You are going to start by betting a penny, and then I roll a 10-sided die. It is labeled 0 through 9. Whatever you roll, that's what I multiply your bet by and give ...
102
votes
15answers
37k views

My wife has died

In 1980, a man lives on the 30th floor of his building. Every morning he wakes up, gets ready, kisses his wife, takes the elevator down to the first floor, and goes to work. One morning, he wakes ...
0
votes
1answer
231 views

Who's the killer? [closed]

When the elevator man saw Mr. Kelley, Mr. Kelley was bleeding slightly, but he did not seem too badly hurt. Mr. Kelley had destroyed Mr. Jones’ business by stealing all of his customers. The ...
5
votes
3answers
229 views

Four squares into many squares

You are given four unit squares and your task is to form as many rectangles as possible out of it starting from 1 square (by overlapping every squares into each other) to N, one by one (2,3,4...). So ...
0
votes
2answers
186 views

Boxes stacked one above the other

Eight boxes, A, B, C, D, E, F, G, and H are kept one above another not necessarily in the order above. Three boxes are between H and G and neither of them is at the top or bottom position. ...
2
votes
1answer
180 views

People having different ages residing on different floors of a building

Here is the riddle: Eight people, 'A', 'B', 'C', 'D', 'E', 'F', 'G', and 'H' live in an eight–story building. The lowest floor is numbered '1' and the topmost floor is numbered '8'. The ...
5
votes
1answer
119 views

To all you Game lovers

If BACKGAMMON is reverse of CONNECT4 And OTHELLO is BACKGAMMON and MONOPOLY together Then TRIVIAL PURSUIT is OTHELLO and what together? The "what" is of course a sit down game! ...
12
votes
2answers
295 views

Pucks in the arena

Two identical pucks of radius 10 cm are placed in a round arena of radius 1 m. They are positioned 50 cm away from the center of the arena on opposing sides. Assuming no energy losses during sliding ...
1
vote
6answers
1k views

A murder in Manchester

Harrison and George are best friends, they both live in Manchester. One day, Harrison goes to George's house to visit him, but after opening the door, he finds his friend dead near the desk, with a ...
5
votes
6answers
630 views

You meet Yessayer, Nosayer, Truther, Liar

You meet 4 persons you haven't seen before, and must ask questions to determine who is who.They know each other, and their friends' behaviour. You may ask each as many times as you want but only yes/...
4
votes
2answers
321 views

A locked room puzzle

“They’re in the drawing room, Sir,” said the constable who was waiting outside the doors. The house — perhaps mansion was a better word — was a square, four storey building in two acres of grounds. ...