This tag is meant for questions about the mathematical principles behind games, riddles, or their possible solutions. If the answer is known to you please do not use this tag to "riddle" other users, but rather to ask about the correctness of a possible solution or ways to extend and improve an ...

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-1
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0answers
50 views

What is the logic and the next numbers in the following sequence? [on hold]

Got this as a question in an IQ test and cannot figure it out, anyone know? 12, 26, 31, 76, 77, 94, 101,...
3
votes
1answer
46 views

The fly and its owner

This is a related problem to Fly and Two Trains Riddle, but must not be confused for a duplicate. A man is taking a leisurely walk with his pet fly at a pace of $v_m$. While the fly is buzzing at ...
0
votes
3answers
63 views

Number theory puzzle

If $(ABCD)÷(DCBA)=9$ where $A,B,C$ and $D$ are distinct and all them belong to ${0,1,2,3,4,5,6,7,8,9}$ but $A$ and $D $are not equal to zero then find $A,B ,C$ and $D$. I tried with the decimal ...
0
votes
5answers
74 views

Given $n$, what function returns $0$ for $n < 1$, but $1$ for all else?

I'm looking for a simple operation that returns $0$ if $n$ is less than $1$, but $1$ for anything greater than or equal to $1$. What does the trick?
1
vote
2answers
32 views

Question involving area and perimeter of two parallelograms sharing a diagonal.

Given two parallelograms $P1$ and $P2$, such that area of $P1$ is greater than area of $P2$, can we say that the perimeter of $P1$ is greater than the perimeter of $P2$ ? Actually I was trying to ...
1
vote
1answer
32 views

The merchant and the fake coin [duplicate]

Next is a riddle that I found interesting and I decide to share it with you. Try solve it by yourself before reading the answer. A merchant has 13 fair gold coins with one fake among them. The fake ...
0
votes
0answers
40 views

Marbles that are distinguishable and indistinguishable at the same time

Thinking about a question and my answer to it and another question I asked earlier. I've come up with the following problem: Consider two otherwise very similar marbles, a red one and a blue one. Let ...
5
votes
1answer
56 views

Intersection of 8 spheres: find the volume

From a long time ago, I remember a puzzle asking for the common area available to four cows: each cow is attached to a different corner of a square with a rope that has the same length as the sides of ...
3
votes
3answers
60 views

Propose an algorithm to find a “celebrity”

A celebrity is a person that everyone knows, but he doesn't know anyone. If we think of a group of people as a graph, where if there is an arrow from $A$ to $B$ that means "$A$ knows $B$", then a ...
-2
votes
0answers
46 views

Confusing Puzzle question. [closed]

Bob makes minimum of 1 painting per day and maximum of 11 paintings per week.Prove that in the next seven weeks, there exists some period of consecutive days where Bob makes exactly 20 paintings. In ...
2
votes
1answer
30 views

how to calculate nth term of mth row of this table?

there is a table which grows as 1,1 1,1,2 1,1,3,3 1,1,4,4,6 1,1,5,5,10,10 1,1,6,6,15,15,20 .....and so on If i want to find an specific element of the table ...
7
votes
0answers
25 views

Display a number using a scientific calculator with most keys are stuck. [migrated]

Your have a scientific calculator such that most of the keys are unable to pressed. The only keys that work are those for the functions $$ x^2 \;\; \sqrt{x} \;\; x!\;\; \exp\;\; \ln\;\; ...
0
votes
2answers
63 views

Area of portion of circle inside a square.

Consider a square grazing field with each side of length 8 metres. There is a pillar at the centre of the field (i.e. at the intersection of the two diagonals). A cow is tied to the pillar using a ...
2
votes
0answers
35 views

Finding a murderer from statements from suspects [closed]

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 ...
0
votes
1answer
47 views

Probability puzzle involving crickets on a chess board

I was given the following problem in a technical interview: Suppose you have a normal 8x8 chessboard, and crickets are placed on every single square. The crickets begin to hop from square to ...
2
votes
1answer
54 views

What's the geometry of a puzzle key called?

Is there a name for the geometry of a classic puzzle key? It's not an ellipse, neither a circle, ...
0
votes
1answer
20 views

Count Shared Customers

GIVEN: A company has multiple "retail" locations (10 as an example). They collect data on customers, so they are able to identify customers that shop only 1 location versus customers that shop at ...
0
votes
3answers
37 views

Swimming pool problem: Time required to empty the swimming pool

In a swimming pool, 6 swimmers have to swim such that 3 swimmers start from end A at intervals of 1 minute and the remaining 3 start from end B at intervals of 2 minutes where A and B are opposite ...
2
votes
0answers
36 views

The $8$-Puzzle and $2$-Cycles

I have been studying the $8$-puzzle and have thus far managed to wrap my head around the following information: The following illustrates the solved position of the $8$-puzzle, where $9$ is the empty ...
1
vote
0answers
42 views

Looking for an alternative solution for the mutilated chessboard problem

Given a mutilated chessboard where two diagonally opposite squares are missing (the unmutilated version of it has $64$ squares), and given $31$ domino pieces, is it possible to cover the entire ...
-1
votes
0answers
13 views

Finding the wrong weight [duplicate]

I have 11 balls of the same weight (unkown) and 1 ball of different weight (heavier or lighter). If i mix these balls together - Given a Balance Scale and 3 TURNS how to find which is the odd ball ...
2
votes
5answers
89 views

A peasant and his cows

A peasant owns $2n+1$ cows. When he separates a cow from the rest of the herd, he can split the $2n$ remaining ones into two groups of $n$ cows such that the sum of weights of each group are equal. ...
4
votes
2answers
83 views

A tale of two palindromes (sum of squares of two palindromes is a perfect square).

I am just curious on wether there are infinitely many palindromes say $p_1$ and $p_2$ satisfying: $p_1^2+p_2^2$ is a perfect square with $\gcd(p_1,p_2)=1$. I believe that there are some but, are ...
0
votes
1answer
36 views

How many different ways can I add three numbers to get a certain sum?

I'm working on a little program and I stumbled across a small math problem I can't quite solve. This is what the program does. A sum is generated. Now, the user can subtract either 3, 4, or 5 from ...
1
vote
1answer
41 views

Find appropriate number fill in the blanks [closed]

Find appropriate number fill in the blanks
3
votes
1answer
48 views

What gambling/board game or real life thing can (surprisingly) be modelled as a linear programming problem?

So I've taken Linear Programming 101. I've read my textbook, took the test and all that, and - besides all the theory, the nice algebraic interpretations, etc - I've encountered a lot of textbook ...
2
votes
0answers
76 views

How to solve instant insanity puzzle with graphs.

So I have a 10 cube insanity puzzle, I constructed the graph (I'll post pc later) based on the colors the problem is that there is just way to many lines and nodes to see the solution. Is there any ...
-1
votes
0answers
40 views

Maths Puzzle ABCDE [migrated]

My younger sister came home from school with this maths puzzle from her teacher, any ideas? because I am baffled... Replace the letters A,B,C,D,E with the numerals 1,2,3,4,5 so that the following ...
7
votes
1answer
1k views

Maths question from an IQ test [duplicate]

It is possible that 25 is the correct answer since I guessed (educated guess) that and got a predication of 170 IQ (obviously not accurate) I saw that 63 + 25 = 88 and 16 + 9 = 25 but then ...
3
votes
1answer
47 views

Numbers interpreted as sets and functions

In set theory numbers are defined as sets $$\emptyset,\{\emptyset\},\{\emptyset,\{\emptyset\}\},\{\emptyset,\{\emptyset\},\{\emptyset,\{\emptyset\}\}\},\dots$$ where $n+1=n\cup\{n\}$ and ...
2
votes
2answers
106 views

Prove a length of 6 in a triangle diagram.

A puzzle: Three equilateral triangles of size 3, 4, and 7 touch at a corner. The other corners of the size 4 triangle are 3 away from a 3 corner, and 7 away from a 7 corner. How far apart are the ...
5
votes
2answers
281 views

logical problem (how long did you walk?)

My wife is very kind, she always picks me up at work by car and drives me home. Today, I finished at work 30 minutes earlier! So I decided to walk home... on the way I met my wife. She was on her way ...
0
votes
0answers
19 views

Systematic Gaussian elimination on a binary matrix?

I am trying to understand the mathematics behind the lights out puzzle (http://mathworld.wolfram.com/LightsOutPuzzle.html). There's a very helpful webpage at ...
19
votes
2answers
406 views

Shortest possible unreachable shape

This is a follow up to Is every shape possible with a snake? . Imagine a 2d snake formed by drawing a horizontal line of length $n$. At integer points along its body, this snake can rotate its body ...
1
vote
1answer
103 views

The sum of $1+1+1+1+…$

My teacher recently showed me a rather weird result and I would like to know if he was just tricking me or if he was serious. He showed me that $g=1-1+1-1+1-...=\frac{1}{2}$ Then he said that ...
-3
votes
0answers
57 views

Crack this sequence [duplicate]

$a_1$=3$a_2$=9$a_3=30$$a_4=101$$a_5=358$$a_6=1443$ I am asked to find $a_n$. I have tried every thing I can think of, method of difference, putting it into a general equation and try to find the ...
0
votes
1answer
51 views

Are the odds one in a million? [closed]

This is a from a card game call Magic the Gathering And my question is regarding this video during a tournament match (best of 5). One in a million. You dont need watch the video I will explain the ...
1
vote
2answers
79 views

Puzzle: With balance scale and four weights totaling 40 pounds, measure any integer weight from 1 to 40 pounds [closed]

A farmer has a 40 pound stone and a balance scale. How can he break the stone into 4 pieces so that, using those pieces and the balance scale, he can weigh out any integral number of pounds of corn ...
57
votes
0answers
7k views

“The Bachelorette Problem” (slightly adapted from Tao's Google+ account) [duplicate]

The following puzzle being very much recreational for me, I couldn't resist myself from sharing it with my fellow MSE user friends. Let's have a look at it. You are the most eligible bachelorette ...
7
votes
5answers
1k views

Hank and his old car

I'm sort of struggling with this riddle told to me by a friend: Hank owns a car. He has been taking good care of his car; In fact, he has been taking such good care of it that the age of Hank, ...
0
votes
1answer
20 views

Counting length of pyramid's sides puzzle

I have four blocks, the first block of length two, the second of length three, the third of length four and the fourth of length five, and I can arrange them in the following way: I am allowed to ...
1
vote
1answer
38 views

Puzzle - Finding which balls are heavy

Puzzle my sister told me about, I've yet to solve it and im open to ideas. You have 6 balls, 2 red ones, 2 blue ones, and 2 green ones. Out of each pair, 1 is heavy and 1 is light (so overall you ...
0
votes
1answer
15 views

A limited composition of two unlimited functions on natural numbers?

Can someone give an example of two functions $f,g:\Bbb N\to \Bbb N$ such that $|\operatorname{Im}f|,|\operatorname{Im}\,g|\notin\Bbb N$, but such that $|\operatorname{Im}\,g\circ f|\in\Bbb N$?
4
votes
2answers
95 views

A puzzle about a sum and product of two numbers

The Gray Man wants to test The Hardy Boys. He says to them, "I've selected 2 positive integers, both bigger than one." He then proceeds to reveal their total and product to Frank and Joe ...
1
vote
0answers
62 views

explaining the pattern

I have been given the following math puzzle: you are given a matrix that is filled by the following rule: every cell i,j is evaluated by taking the lowest non-negative number that is not present in ...
9
votes
2answers
155 views

Is every shape possible with a snake?

Imagine a 2d snake formed by drawing a horizontal line of length $n$. At integer points along its body, this snake can rotate its body by $90$ degrees either clockwise or counter clockwise. If we ...
1
vote
1answer
46 views

How do you calculate 45 min without any clock and sense of time? [duplicate]

There is two non uniform,unequal ropes. Every thing like weight,length etc are not same. But one thing is same. Each one is burned down within 1 hour. I'm giving you these two ropes and a candle just ...
18
votes
2answers
485 views

Is it true that we can get zero for all $(x,y,z)\in\mathbb{N}^3$?

There are three distinct positive integers $x$, $y$, and $z$. We can choose two numbers $a,b\in\{x,y,z\}$, where $b\leq a$, then replace $b$ by $2b$ and replace $a$ by $a-b$. Is it true that there ...
0
votes
1answer
31 views

Progressive Matrices Puzzle

I have this mind puzzle which has bothered me the latest days. QUESTION: CHOOSE ANSWER: . I realize that there are relations (rotation and translation) between three pairs of the matrices (1-4, ...
6
votes
6answers
933 views

A number when divided by 2, 3, 4, 5, 6 leaves a remainder of 1 but it is divided by 7 completely.

I came across a question which is as follows: Find out the smallest number which leaves remainder of 1 when divided by 2, 3, 4, 5, 6 but divided by 7 completely. What I did is given below step wise. ...