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Questions tagged [mathematics]

A puzzle strongly related to mathematical facts and objects, or whose solution needs serious mathematical arguments. General mathematics questions are off-topic but can be asked on Mathematics Stack Exchange.

3
votes
2answers
151 views

100 prisoners' names in boxes, against smart warden

My question, which I do not know the answer to, concerns the classic 100 prisoners and 100 boxes puzzle, summarized below. The solution to this assumes the names are placed in boxes randomly, and gets ...
0
votes
1answer
86 views

Arranging people in groups at a conference

54 people attend a conference. There are 6 tables that each seat 9 people. Each table has a different topic and all 54 people have to move around and sit at each table. Can you advise a formula as ...
-2
votes
2answers
137 views

All Unique Permutations [closed]

We have the word: RAPSEVNOBLURKANIWA We want to find the number of unique permutations that could be made with RAP always staying together, so that there are: no 3 adjacent consonants, ...
5
votes
2answers
126 views

Bracket schedule

my friends and I are doing beer Olympics. There are 12 teams with 6 games. Each game has its own “bracket”. Essentially there will be 6 winners, 1 from each bracket or game. Those teams will then ...
1
vote
1answer
302 views

Distance from One

For random natural number $N_0 > 1$, we find $N_1$ by the rule: $N_{i+1} = \frac{N_i}{2}$ if $N_i$ is even $N_{i+1} = 3N_i + 1$ if $N_i$ is odd If $N_1$ isn't equal to $1$, we find $...
7
votes
1answer
165 views

How many times does the earth rotate per year?

Assuming there are exactly $365$ days per year. How many rotations about its axis does the earth make in one year?
1
vote
2answers
265 views

The result is 7 game

The goal of this game is to find the lowest score for the 10 equations below. 0 ? 0 ? 0 ?...
-3
votes
2answers
116 views

Arrange StakExchangePuzzling [closed]

Find the total number of permutations of the word STAKEXCHANGEPUZZLING such that the letters STAK always stay together. Rules: No 3 adjacent consonants, no 2 adjacent vowels. For every odd pair of ...
0
votes
0answers
88 views

Can you Solve it [duplicate]

----- + ----- + -----= 30 Use only (1,3,5,7,9,11,13,15)
14
votes
2answers
349 views

Construct $\sqrt{3}$ using every natural number

Construct $\sqrt{3}$ using every natural number $n\in \mathbb{N}$ (1, 2, 3, 4...) exactly once and the operations addition ($+$) and division ($\div$).
5
votes
3answers
467 views

Puzzling Equations

Mathematics is a fascinating field of study, ever changing, far from finished. Arbitrary symbols, prescribed with special meaning become extraordinary challenges for the mind. And if you’re like ...
2
votes
0answers
70 views

I have a good question for thinkers out there. Mr. Mike's Retirement Party [duplicate]

When Mr.Mike finally retires, he is going to have a party on a cruise ship with all 12,184 of his former students. Each of the students will be given a number as they board the carrier. All his former ...
8
votes
1answer
421 views

A case of the sniffles

The cubicle farm at the Colla-R water treatment plant is laid out in a neat square: eight rows of eight cubicles with a narrow corridor between each cubicle (in the diagram the thin black lines are ...
8
votes
1answer
197 views

A Number Game puzzle

Our team has created 9 math puzzles with ranging difficulty. Let me share one of them. At the beginning a number is given to you. Your objective is to get a different number by making choices. Here's ...
9
votes
4answers
343 views

Not-Quite-Sufficiently-Advanced-Technology Square

This was given as an assignment to a group of sixth graders, who were told they could use calculators. Beyond that, no real assistance was provided. They were not working on it as a group, so ...
5
votes
1answer
259 views

Unlock my phone! March 2018

New month, new password, but I've already forgotten! Help! What is my phone's password this month? Hint #1: Hint #2:
7
votes
1answer
300 views

Where did the mathematician go?

Two mathematicians were discussing their recent holdays. The first mathematician exclaims I was on an all inclusive trip to lanserote for two weeks. The second mathematician, slightly ashamed, ...
6
votes
2answers
224 views

“Balls in Boxes in a Sack” Weighing Problem

This puzzle is based on a competitive programming problem in SG NOI 2019. Let's assume there are $100$ balls with some labels (e.g. with $100$ different marks on them) having different weights of ...
0
votes
1answer
148 views

Fastest Way To 6 Pawns On the B To H Files

This is an old question with anwser to the optimal solution get 6 pawns on the A-File: Get 6 pawns in file A or H Since I’m really into chess theory, I decided to find fastest solutions I could find ...
10
votes
1answer
1k views

Island of Liars

A king goes to an island, where there are 5823 people who always tell the truth and 8723 who always lie. The king is special guest for the party celebrating 2053 year. On the party, liars and ...
12
votes
1answer
464 views

Find the next number in this sequence

Find the next number in the sequence : 1; 5; 33; 25; 2; 16; 14; 12; 11; ? What is the next number and why ?
3
votes
2answers
613 views

Bridge building with irregular planks

Imagine you have a big rectangular pond in your back garden. You wish to build a bridge from your house in the lower left corner to the small pagoda in the top right. You have lots of planks of ...
10
votes
9answers
7k views

Why would five hundred and five be same as one?

Grandpa was in his crazy math mood again. "using rot13 and your math knowledge prove to me that 505 = 1" He said. Really? Can you? HINT
10
votes
1answer
388 views

Zero, One, Two, Three, etc

Find a solution to the following system of simultaneous equations. All letters stand for integers (positive, zero, or negative), and different letters are different integers. The preferred solution ...
4
votes
2answers
280 views

How to make 18 from 1, 3, 4, 8

This question was on my sister's 5th-grade homework, practicing order of operations. It was to make 18, using the numbers 1, 3, 4, 8 and the operations +, -, and *. The instructions imply using each ...
6
votes
1answer
653 views

My friend is being a hypocrite

So I was having an argument with a friend and I know I'm right, but she just won't admit it and it's getting really irritating. She thinks this thing goes one way when it clearly actually goes down! ...
12
votes
2answers
2k views

My Graph Theory Students

I have 18 students in my graph theory course this semester: Anne, Bernard, Clare, David,..., and Rachel. At the start of the course I asked them to draw the graph below, in which each of them is ...
9
votes
1answer
165 views

What's the significance of this pattern?

Note, this is my first submission, let me know if I broke the rules. What is the significance of the following sequence of # signs? ...
29
votes
4answers
4k views

Happy pi day, everyone!

A baker is working a batch of dough. He shapes it into a cylinder of height a and radius z. What will the baker make from this volume of dough?
34
votes
7answers
5k views

Who is our nearest planetary neighbor, on average?

Assume that the planets have circular orbits centered on the sun. Assume that the radius of the orbits is 0.39, 0.723, 1, and 1.524 for Mercury, Venus, Earth, and Mars. Assume also that there are no ...
11
votes
3answers
648 views

What's the combination for the safe?

The CFO sat back in his leather chair, which creaked and squeaked. "It's actually pleather," he said to the intern sitting nervously opposite him, a notepad resting on his knees. "We're very cost-...
3
votes
1answer
184 views

Albrecht Durer Inspired Magic Square

A magic square is an n-dimensional matrix in which each row, column, and main diagonal sums to the same 'magic number' (denoted by s). A normal magic square uses each of the numbers from 1 to n ...
-2
votes
1answer
165 views

How to solve this puzzling?

20190309,245111132328,331508165892,51222189610023,? A friend of mine gave me this number puzzling but I have no idea what is the logic. Does anyone know how to solve?
5
votes
5answers
637 views

The Pebbles Quiz

We are in a TV game. We have 8 same looking boxes, each of which has 2 pebbles. Each pebble could be either precious or not precious. We choose a box and the host, without looking inside the box, ...
6
votes
2answers
222 views

For what x can we solve $1,2,3,x=5$

This is a variation on the formation of numbers theme. Given $1, 2, 3, x$ in order, and the operations plus, minus, times, divide, and brackets, what single digits can x NOT be? i.e. find a ...
4
votes
1answer
238 views

Numbers Brain Teaser

I've come across a strange brain teaser on one of those sheets with things like: (man overboard) So here's the puzzle: 0 - 20 10 - 3 14 - 29 96 - 72 1977 I've been trying to ...
-3
votes
3answers
238 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:
11
votes
2answers
317 views

Geometry From Hell

You’re locked in a room with nothing but a pencil, a math compass, and paper. You do not have a straightedge. Your captors have informed you that you cannot leave until you construct (the endpoints of)...
-2
votes
3answers
109 views

Get 2 liters from 4 and 5 liter buckets [duplicate]

You have a 4 liter bucket and a 5 liter bucket and an (infinite) supply of liquid. How do you get 2 liters?
8
votes
4answers
2k views

Number of folds to form a cube, using a square paper?

Take a square paper of size S X S units, and thickness of paper 1 unit. How many half folds should we do to get form a cube out it? Consider infinite foldable paper.
5
votes
2answers
1k views

What's Bob's age again?

I created this problem myself, but I did have inspiration. Today is a special day, I'm moving out of my parent's house. My father comes to me and says "Wow, you're half my age. On the day we moved ...
2
votes
2answers
126 views

Cyrus' Adventure (Part 5)

Cyrus walked through the third door and went into a damp passageway. Suddenly, Cyrus found a big bug on the floor. "Damn!" Cyrus stepped on it and the bug died. After a while, Cyrus arrived at a small ...
4
votes
1answer
296 views

Chess Massacre Variants-Play Find The Fastest Way?

I have thought up several variations of massacre chess. Massacre chess is a game where almost every single move is a capture. The idea here is that only the chosen type of piece can capture. It ...
14
votes
3answers
563 views

Waiting for the gravy at a dinner table

You are sitting at a round dinner table with $N$ other people (i.e. $N+1$ people all together). One of the other guests is the first to pick up the gravy boat and pour some on their potatoes. It then ...
6
votes
2answers
490 views

I'm trying to create a magic square

I'm having trouble trying to make a $3\times3$ magic square with magic number $12$ and I can't figure it out. Can you please help me?
4
votes
2answers
243 views

By American Standards

I once went to the USA and a guy asked me, "What is a+B?" I could answer him. What was my answer? HINT: Note: The title is appropriate, and B is capitalized on purpose.
17
votes
2answers
475 views

Maximum Height of a Hotel with Strange Elevators

I encountered this puzzle many years ago, and I think back on it often as it is unique and thought provoking. As far as I know nobody has proved the given solution as optimum, so it may still be ...
0
votes
2answers
113 views

Chess tournament winning streaks #2

So I asked a question here, which asks how many ways there are to score 7 points in 7 chess tournament games using the system on lichess.org, outlined both here and in the original question. That was ...
6
votes
7answers
308 views

Find minimum number of meeting periods to reach 2 degrees of separation for a group [closed]

I am running a training course and I want to arrange a set of 1:1 meeting periods between the participants such that at the end of the day there is a maximum of 2 degrees of separation between any of ...
9
votes
1answer
281 views

Chess tournament winning streaks

On lichess.org, they use a points system for keeping track of who is winning in a tournament. A win is worth two points, a draw is worth one point, and a loss worth zero points. Once a player has ...