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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1answer
27 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
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1answer
10 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
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2answers
85 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 ...
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0answers
41 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 ...
4
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1answer
69 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
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1answer
40 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 ...
6
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1answer
141 views
+100

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
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1answer
27 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
617 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. ...
0
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1answer
28 views

Rigorous proof for a maximization problem

Problem: Eight players entered a round-robin tennis tournament. At the end of the tournament, a player who wins $N$ sets will take home $N^2$ dollars. The entry fee is $17.50 per player. Why is this ...
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1answer
36 views

Can this be proven for any maze?

http://9gag.com/gag/aKgrQDj Is there a maze that can't be solved simply by following that strategy. Assumption Solution must exist Sticking your hand to the right or left don't solve that.
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2answers
67 views

puzzle series (need help)

Can you give a hint on this puzzle please? \begin{align*}5+3+2&=151022\\ 9+2+4&=183652\\ 8+6+3&=482466\\ 5+4+5&=202541\\ 7+2+5&=?\end{align*}
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0answers
26 views

Optimal size of n circles to fit an area given their relative sizes

Let us say that I have a rectangular area that has to always look "filled" with circles. (the void spaces with the given number of circles should be minimal)(Goal) Let us assume that, I am also told ...
7
votes
1answer
340 views

A gameshow logic puzzle

A friend posed this puzzle to me a few months ago, and it has tortured me ever since. The puzzle goes something like this: Suppose you're on a gameshow, and there are three doors: two doors have a ...
10
votes
2answers
209 views

Gardner riddle on mathemagicians

A cute riddle (but maybe not so easy!) from Gardner: At a gathering of mathemagicians, the Grand Master and his 8 disciples are seated at a round table. The Grand Master will judge each of his ...
15
votes
3answers
326 views

Is it possible to uniquely number faces of a hexagonal grid with consecutive numbers?

You have a grid of regular hexagons. The aim of the game is to have each hex contain the numbers 1-6 on its edges. Each edge must also be connected to another edge that has a value one higher and ...
0
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0answers
33 views

logic problem/puzzle solving [migrated]

I'm here to ask you if it is possible to find a way to solve this problem. I'm designing the puzzle-enigma section of a video game and try to find possible solutions and mechanic for it. Imagine each ...
2
votes
0answers
54 views

A river crossing puzzle with relatively prime problem

I want to share a problem on a facebook group : https://www.facebook.com/groups/419858384791916/permalink/640398286071257/ 99 people, numbered 2 to 100, are all on one side of a river and wish to ...
2
votes
1answer
69 views

Three people want to personally meet each other as fast as possible: optimization problem.

Problem: Three people want to be all gathered at the same place, and they want it to happen as soon as possible. Where should they head to? P.S. Assume they all travel with the same speed. Think of ...
2
votes
2answers
86 views

Solving Rubik's cube and other permutation puzzles

I've seen two questions on solving the Rubik's cube but none of the answers have given a complete solution using mainly mathematical techniques. Furthermore, I've not seen a good explanation of ...
2
votes
1answer
52 views

math in horseshoe puzzle

We know that Rubik's Cube is a good demonstration of group theory. Correspondingly, for the horseshoe puzzle as in the picture below, is there a math language for it? Does it demonstrate any math ...
10
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1answer
217 views

Bidding Tic Tac Toe

In regular tic tac toe, both the players get alternate chances. This is a variant of that. Player $A$ has $\$x$ amount and player $B$ has $\$y$ amount as initial balance. Assume that $y>x$. Both ...
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2answers
52 views

Minimum number of moves in Chocolate Puzzle

I've seen this problem on an algorithms competition and although there is an explanation on the website, I couldn't understand it. The abridged problem statement is as follows: Suppose you have two ...
1
vote
1answer
11 views

Figuring out the amount of 'straight edge' pieces in a puzzle?

I was wondering if there was any set way to determine the number of 'straight edge' pieces in a puzzle, assuming the pieces are all in neat rows and columns? Does the ratio of edge pieces to middle ...
2
votes
3answers
126 views

Simple puzzle from The Moscow Puzzles with wrong solution?

I have a book of mathematical puzzles -- The Moscow Puzzles, edited by Martin Gardner -- and I'm struggling to make sense of the following puzzle. It seems utterly simple, yet the solution given seems ...
0
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2answers
73 views

Points on a sphere puzzler [closed]

For a perfect sphere that has $n$ random points on it's surface: is it possible to connect all the points on the surface with geodetic segments around the surface of the sphere such that each point ...
0
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0answers
63 views

Algorithm to calculate powers

Is it possible to write an algorithm that uses only multiplication and addition to calculate $a^b$ where both a and b are real numbers?
2
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1answer
180 views

Game between 2014 card players where everyone with at least 2 cards passes a card to each of his neighbors

2014 card players sit around a big table. One of the players begins with 2014 cards on his hand, and the other have none. The rules for the game are: Every minute shall every player, who ...
1
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2answers
315 views

Could one be a friend of all?

The social network "ILM" has a lot of members. It is well known: If you choose any 4 members of the network, then one of these 4 members is a friend of the other 3. Proof: Is then among any 4 ...
2
votes
2answers
54 views

Cracking license plate checksum

Suppose a city has license plates assigned to cars with 7 digits $a_1$ to $a_7$ and a checksum calculated by the following algorithm: ($m_k$ are integers) $$m_1a_1+m_2a_2+\cdots+m_7a_7\mod 28$$ (which ...
0
votes
4answers
1k views

Math Riddle in Combinatorics.

A blind man is on a strange island and he has 2 red pills and 2 white pills, completely identical and has kept in his pockets, he needs to take 1 red pill and 1 white pill order doesn't matter. If he ...
8
votes
1answer
367 views

Puzzle: Give an algorithm for finding a frog that jumps along the number line

You are playing a game, your goal in this game is to catch a frog that's leaping between natural numbers. At first, the frog is found at the number $a \in \mathbb N$ which is not known to you. Each ...
21
votes
8answers
3k views

There is a subset of positive integers which no computer program can print

It's said that a computer program "prints" a set A ($A \subset \mathbb N$, positive integers.) if it prints every element in A in ascending order (Even if A is infinite.). For example, the program can ...
21
votes
5answers
1k views

Chicken Problem from Terry Tao's blog

This problem was posted by Terry Tao in his blog earlier. It's actually from his son's Math Circle. It took him $15$ minutes to solve it. I guess we all can take a crack at it. Three farmers were ...
0
votes
2answers
64 views

Combine four '4' and the basic operators to get 20 [closed]

4 4 4 4 ÷ × + - Using these operaters how to get answer 20.
1
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2answers
90 views

Algebraic solution to the Broken Weight Problem

Here is a problem I was sent, which it turns out was first posed by Claude Gaspard Bachet de Méziriac in a book of arithmetic problems. The problem is as follows: A few years ago, a King's ...
5
votes
1answer
82 views

Number of valid NxN Takuzu Boards a.k.a 0h h1 (details inside)?

Takuzu a logic puzzle which has a NxN grid filled with zero's and one's following these rules: 1) Every row/column has equal number of 0's and 1's 2) No two rows/columns are same 3) No three ...
2
votes
1answer
121 views

Is this a correct solution to determine as to whom I should invite for the party?

I was working my way through some Propositional Logic Questions in Discrete Maths by Rosen, when I came across the following question: When planning a party you want to know whom to invite. Among ...
2
votes
1answer
125 views

3 dimensional $6\times 6\times 6$ lit cube problem involving looking for a specific lit pattern and quantity of them.

Suppose we have a $6\times 6\times 6$ cube such that it has $216$ subcubes, each with a visible, discernible light in it. A random number generator is connected to the cube and it will choose ...
1
vote
1answer
32 views

Finding the count of paths with K turns from corner to corner in a square box

I'm having trouble understanding the solution given for the problem here: http://www.codechef.com/DEC11/problems/MOVES/ Given a square table sized $N \times N$ ($3 ≤ N ≤ 5000$; rows and columns ...
1
vote
1answer
98 views

Is this a correct solution to determining which of two people is the liar using one question?

I am a newbie to Stack-Exchange and if there is any problem in my question -- I apologize beforehand . I was working my way through some Propositional Logic Questions in Discrete Maths by Rosen , ...
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3answers
85 views

How can you use the digits 2 0 1 5 to equal 28 [closed]

you can use the numbers only once and have to use them all.
1
vote
1answer
43 views

Pebble Problem Maximum$=\big\lceil \log_3(n)\big\rceil$?

In the pebbles problem, you are given $n$ number of pebbles that has one of the $n$ weigh less. If you are given a balence that you can you $k$ times, what is the minimum amount of $k$? ...
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votes
1answer
113 views

Why is it possible to find the birth year by subtracting one's age from 114?

I noticed that any person can find their birth year just by subtracting their age from the number $114$. For example, if I am $25$ years old then from $114-25=89$ I know the birth year is $1989 $. ...
4
votes
1answer
57 views

Puzzling Sequence

Today I was given a question that first I thought might be easy to solve but then no matter how hard I tried I couldn't solve it.(It's not really related to maths just some puzzle) if: $$ 9999=4\\ ...
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2answers
57 views

Scores of six soccer matches

In the first round of the city soccer tournament, the teams in group A finished as follows: ...
0
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1answer
45 views

How to find a recursive formula for some sequence

I know how to find a non-recursive formula for a recursively defined sequence. However, now I have this puzzle which gives me a sequence (but not the recursive definition) and challenges me to find ...
4
votes
1answer
97 views

The Island in the Miracle Sea. (Christmas edition)

To all of you who love math like me, I have this puzzling riddle that I hope you find interesting : On Christmas Eve just after midnight, Santa was riding his sleigh over the Miracle Sea when ...
3
votes
1answer
64 views

Knuth's algorithm for Mastermind question

I'm reading about Knuth's algorithm to solve the mastermind game, so I've looked in wikipedia and read the pseudo-code (http://en.wikipedia.org/wiki/Mastermind_(board_game)#Five-guess_algorithm). I ...
3
votes
2answers
52 views

Objects into two bags puzzle

I found a maths puzzle somewhere and a part of it as below: Kelly wants to place n objects $a_1,a_2,⋅⋅⋅,a_n$ into two bags. For each $i=1,2,⋅⋅⋅,n$, the weight of $a_i$ is $w_i$ kilograms. The ...