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8
votes
2answers
557 views

How to let all people in Group A talk to all people in Group B in a shortest amount of time?

Ok, let say Group A has N number of people, and Group B has M number of people. I want each person in Group A to have a fixed T time conversation ( time T is fixed like 5 min or 10 min) with each ...
11
votes
1answer
608 views

origin of the “missing dollar puzzle”

I am wondering when the missing dollar puzzle first appeared. I am sure I read it forty years ago or so, but maybe it is much older. Does anyone knows it?
3
votes
1answer
265 views

Non-Diagonal Pointing Problem

You can see the rules for pointing problem at this article. It has been clarified that there is no solution to this question. But, what if we remove the diagonal rule? is there any solution?
12
votes
1answer
6k views

Write digits 1 to 9 in the table, each pointing to next 3x3 grid

Write 1 to 9 digits in an empty Sudoku table with these rules (similar to 9-Queen problem): There are 9 Boxes indexed from 1 to 9 in the image below. and each box has a 3x3 grid child. Every two ...
13
votes
2answers
1k views

Horses and Tracks

I have seen this question before and I am intrigued that there might be various ways it can be solved. I do know of one way, but I am trying to find out if there is any other approach possible. The ...
26
votes
2answers
2k views

Where has the last dollar gone?

Lately I have found different versions of this puzzle, I was wondering if it has a name or belongs to a specific kind, so that I can understand it better. Here it is: Peter got \$10 from his father,...
10
votes
2answers
2k views

Two Card Probability Problem

I came across this puzzle somewhere on the interwebs. Has stumped me for an answer for quite sometime. Helpplease? Someone picks, at their will, two cards from a deck of cards. The cards have ...
6
votes
1answer
2k views

Find the next symbol in this sequence

I just came up with the following puzzle. I don't think anything like this has been asked here before, but I may be wrong. What's the next symbol in this sequence?
17
votes
2answers
19k views

Difficult IQ test question: What is the box suggesting?

I found a Very Difficult IQ Test on web. One of its questions is: What is the box suggesting? I have seen the answer but there was no clues for the logic behind that. 123456789 176h54308 627456934 ...
7
votes
1answer
830 views

About Grelling's Paradox

Grelling's Paradox is about certain types of words. An adjective is heterological if it does not describe itself; like 'long', 'German', or 'monosyllabic'. An adjective is autological if it does ...
55
votes
4answers
9k views

Interview Question or Pathbreaking puzzle

I thought this changes the way series of numbers are looked at 1 1 1 2 1 1 2 1 1 Write down the next three lines
1
vote
3answers
2k views

A square and a circle at once [closed]

Can you draw something on a piece of paper that looks like a square and a circle at the same time? ( without using Math or 3-d visualisation techniques)
13
votes
1answer
687 views

What drives the brain when creating puzzles?

From as far back as psychologists Robert Sternberg, and Janet Davidson argued that solving puzzles entails the ability to compare hidden information in a puzzle with information already in memory, and,...
10
votes
1answer
2k views

Of men and hats

There's an obvious generalization of this problem: There are a rather large number of prisoners, each of them seeing the color of the hat of all the following sad fellows bot not their; the hats may ...
160
votes
1answer
8k views

Chaos and Order: a visual puzzle in stained glass

I created a visual puzzle, which my wife then implemented as part of a stained-glass window. I've no idea if it is (a) obvious, (b) stupid or hopefully (c) extremely clever, and hence would love to ...
6
votes
1answer
647 views

Decrypt the following message: 5, 18, 92, 6, 1 [Clues inside]

The task is to decode the following: 5, 18, 92, 6, 1 Clues: It's my name [my name is Jake] "Gliding o'er all, through all, Through Nature, Time, and Space, As a ship on the waters advancing, The ...
9
votes
1answer
841 views

Decrypt the code and find the text

Break the rule of the following code and find the original text. 4844026700420337026680789437084266769043634877 3123111411311124132311313221113123421112223234 ...
16
votes
2answers
813 views

Santa Claus flies to the South Pole

It is a little known fact that Santa Claus is in fact a vampire. Why else would he spend so much time near the North Pole and travel only at night? Yes, he fears daylight! His problem is that ...
4
votes
2answers
2k views

A modified version of apples and oranges logic

Question: You have 3 baskets, one with apples, one with oranges and one with both apples and oranges mixed. Each basket is closed and is labeled with ‘Apples’, ‘Oranges’ and ‘Apples and Oranges’. ...
3
votes
2answers
465 views

find the order of fruits

There are five fruits (Apple, Banana, Pineapple, Orange and Watermelon) that should be ordered in their places. But we do not have enough containers for them: there are only two bowls and two baskets. ...
-8
votes
6answers
807 views

Three Wise Monkeys and a Crime [closed]

Is there any crime the three wise monkeys (who see no evil, hear no evil, and speak no evil) could collectively "witness" and not be able to indict the suspect?
9
votes
2answers
2k views

Integer grid problem

I found this programming related problem too difficult for me. The problem asks to find 16 integers and form a 4x4 grid $$\left(\begin{array}{cccc} n_1 & n_2 & n_3 & n_4 \\ n_5 & n_6 &...
10
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 ...
-1
votes
1answer
498 views

Products of three primes that bound RSA numbers [closed]

Let $N$ be some number. Let $R$ and $S$ be semiprimes (ie, each is a product of two prime numbers) such that $R \le N \le S$. For quite a few numbers $N$ we can find $R, S$ such that $S-R$ is small;...
8
votes
2answers
2k views

Entangled physicists

The anti-intellectuals have won the war, and under the iron rule of emperor Nonotin anyone who has been deemed too smart for their own good has been brought to labour camps. But most of the science ...
1
vote
2answers
2k views

Find the order of students presentation(logical puzzle)

Four students P, Q, R and S each working under the super vision of one of the four professors A, B, C and D made their final year MBA Project Presentations one by one, one each in the areas of Finance,...
5
votes
1answer
777 views

Find the pattern of matrices

fill the matrix correctly and the guess the Letter and number of 5th matrix: PS: I'm sure you won't need options!
14
votes
3answers
2k views

The defective clock

James has a defective clock in his room. The clock is digital, and some of the seven bars on its units digit are broken. A bar that works is on when it should be and off when it should be, whereas a ...
3
votes
1answer
458 views

How to control the whole board with 8 standard pieces?

How to control the whole board with 8 standard pieces (one king, one queen, two rooks, two knights, two bishops)? P.S. A piece doesn't control a cell simply by staying on it, so another piece must ...
3
votes
1answer
2k views

is there any sudoku puzzle combined with magic square?

As everyone know in Sudoku sum of each row and column is 45. so all Sudoku solutions are some kind of magic square. but my question is: Have anyone seen a Sudoku puzzle combined with the magic ...
2
votes
1answer
2k views

Find the next number in the series?

Find the value of 'a' and 'b' in the following series. 100,101,120,103,410,321,205,404,60a,5b2
9
votes
2answers
4k views

Color the Table

Color each cell of the table with following rules: Yellow and Orange cells are adjacent, but Red and Black are not. Cell with number 3 is White, Green, Blue or Red and the cell with number 5 is not ...
7
votes
3answers
38k views

Split 12 liters in half with 5 and 8 liter bottles [duplicate]

You have 12 liters of apple juice in a 12 liters bucket and you want to share it with your best friend. But you have an empty 8-liter and an empty 5-liter bottle. How do you split the apple juice in ...
15
votes
1answer
4k views

The seven piece silver chain

You have to stay for 7 days in a hotel outside your city. But you forgot to bring your credit card and are out of cash. You have a silver chain with 7 links. The rule in this hotel is that residents ...
104
votes
16answers
1.1m views

Two doors with two guards - one lies, one tells the truth

You are a prisoner in a room with 2 doors and 2 guards. One of the doors will guide you to freedom and behind the other is a hangman --you don't know which is which. One of the guards always tells ...
4
votes
1answer
620 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 ...
-2
votes
1answer
754 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
2answers
1k views

What is the purpose of a weird non-linear watch dial that goes up to 100? [closed]

Can anyone tell me what is the purpose of the outter dial of this watch? Notice how the scale is not linear and goes to 100. It can only be rotated counter-clockwise only. This is the only picture I ...
7
votes
1answer
566 views

A cube puzzle (Multiple of 6)

If you have a cube, say, $3 \times 3 \times 3$, you know that mathematically it's made of $27$ ($3*3*3$) smaller cubes. Now, just remove one full line of smaller cubes (in this case, 3 smaller cubes). ...
2
votes
1answer
4k views

Confused about step 5 of official Rubik's 3x3 Cube solution

Solution guide: http://rubiks.com/uploads/general_content/Rubiks_cube_3x3_solution-en.pdf I can get to this point pretty reliably now, but when I try the method shown I'm just as likely to go from ...
3
votes
2answers
1k views

Unknown Consecutive Integers Puzzle

Two people, Anne and Bob, each hold an index card. A positive integer is printed on each index card, and these integers are consecutive (i.e. Anne's card may display 8 and Bob's card 7). Anne and Bob ...
22
votes
4answers
3k views

The Monty Hall problem

I'm amazed that, although well known, this problem hasn't been posted yet. Monty Hall You are on a game show. The host of the show shows you three doors. He tells you that behind one of them, is a ...
7
votes
5answers
2k views

Three 50/50 guesses

Three friends enter a quiz-show as a team, the final round of the show is all or nothing, they only get their prize if they can win this round. Three boxes labelled 1, 2 and 3 are placed in a room, ...
24
votes
3answers
6k views

The lake monster

You are on a rowboat in the middle of a large, perfectly circular lake. On the perimeter of the lake is a monster who wants to eat you, but fortunately, he can't swim. He can run (along the perimeter)...
9
votes
3answers
659 views

Generalizing the “shooting puzzle”

Inspired by this puzzle. You have $n$ shooters having a duel, labeled $1, 2, ... n$. Each shooter has an accuracy of $k_n$, with each $k_n$ some probability in $(0,1]$, with $k_1 < k_2 < ... &...
15
votes
1answer
2k views

Is this a new kind of liar puzzle?

I would like to ask if anyone has seen elsewhere this variation on the standard truth tellers/liars kind of puzzle. In the usual repertoire it is assumed that every person questioned knows the answer ...
3
votes
2answers
521 views

Find a high-scoring 53-digit prime number chain

Let a “number chain” be a series of numbers, $n_0, n_1, ... n_{m-1}$ for some $m$, such that in base 10 the low digits of $n_i$ match high digits of $n_{(i+1)mod m}$. For example, after the number ...
6
votes
7answers
7k views

Help understanding the solution to a “shooting puzzle”

I need help understanding the solution to the following puzzle: Puzzle: There is a "triangular" duel between the three shooters. Everyone shoots one by one, can shoot once and any person he wants. ...
3
votes
2answers
2k views

Find shortest network connecting four points

Given the figure below, find the shortest network of straight line segments (like a Steiner tree, or like parts of a Delaunay triangulation) that connects the four circled points while staying in the ...
2
votes
1answer
410 views

Make a wide tower of bridge-shapes

In this question, bridge stands for the illustrated convex quadrilateral, constructed from three equilateral triangles. Letters A, B, C, D, E are assigned to each unit length of periphery as shown in ...

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