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.

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0
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1answer
76 views

Place Your Bets 3 , last of the series

A harder sequence to figure out... What are the next 4 cards, including suits?
2
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1answer
84 views

Place Your Bets - in sequence, of course

Your Puzzle There is some sort of pattern in cards below. Simply figure out what the next card should be. Note: You cannot re-use a card already in play.
3
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2answers
92 views

A Wine Problem for Puzzlers [duplicate]

Simple Follow the instructions on the label. In case you the image is too small, Given three bottles: 8, 5 and 3 liters capacity, divide 8 liters in half (4 + 4 liters) with the minimum number of ...
-3
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1answer
231 views

Repeating decimal. 0.01234567901234

Express the repeating base-10 decimal number $ 0.0123456790123456790... $ as a fraction $ \dfrac{1}{x} $ in any base system up to hexadecimal such that $ x $ has a minimal number of only 0s and 1s.
4
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1answer
792 views

Number of seconds in 6 weeks

Using only 3 characters (any single digit or one of the following operators: $ +,\, -,\, \times,\, \div,\, ! $), construct an expression that evaluates to the number of seconds in 6 weeks.
0
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1answer
92 views

Why do I always lose? [duplicate]

As always, good luck! Sarah is really good at math. I mean, really good at math. Every now and then we play this game where we take turns picking random numbers between 1 and 10, and we add these ...
0
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17answers
5k views

I’ve officially counted to infinity! [closed]

Sarah called me today and explained that she had counted to infinity. I shrugged and said it was impossible. She said that since I didn’t believe her, she would do it again, and this time in only ten ...
7
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3answers
217 views

Groundhog Puzzle [duplicate]

A groundhog has made an infinite number of holes one metre apart in a straight line in both directions on an infinite plane. Every day it travels a fixed number of holes in one direction. A farmer ...
18
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5answers
864 views

Primes less than 100 in a 4 x 4 board

Place one of the digits (0 to 9) in each of the cells of a 4 x 4 board so that as many as possible of the 25 primes less than 100 divide at least one of 10 positive 4-digit numbers that can be read ...
6
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2answers
187 views

Just a Simple Number Crossword

I made a small number crossword for my mathletes club that I thought I'd share. It's not too hard, I think it's just right for a coffee break. Have fun! (Edit: No answer has a leading zero)
0
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1answer
129 views

How much did he pay for the car? [closed]

A man withdrew half the money that was in his bank account to buy a second-hand car, then sold the car two weeks later, receiving only three-quarters of the price he had paid for it. When he paid the ...
6
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1answer
199 views

What kind of puzzle this is?

I received this picture, and the sender told me that it means something?
4
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3answers
789 views

Scheduling based problem

Can you place these numbers into 5 rows of 4 such that each row totals 20? 1, 2, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 6, 6, 7, 8, 8, 8
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15answers
5k views

What is ls Largest Number Formed by only moving two sticks in 508?

Tilting the Image is not allowed. You can cannot change order of digits. You cannot change the Size if Digits unless you are harry potter. You can increase or decrease space between digits though. ...
18
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9answers
1k views

One-one communication

5 people are standing in a circle - person A needs to tell his salary to person B, but none of the others should know A's salary. How is this possible, if every person only whispers to the person on ...
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2answers
101 views

Max pieces to cover a chess board [closed]

Number of individual chess pieces to cover all chess board
4
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6answers
2k views

Find 108 by using 3,4,6

Assemble a formula using the numbers $3$, $4$ and $6$ in any order to make 108. You may use the operations; $x + y$ $x - y$ $x \times y$ $x \div y$ $x!$ $\sqrt{x}$ $\sqrt[\leftroot{-2}\uproot{2}x]{...
4
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2answers
241 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
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1answer
99 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
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2answers
149 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
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2answers
155 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 ...
2
votes
1answer
323 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 $...
8
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2answers
263 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?
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2answers
330 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
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2answers
122 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
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0answers
98 views

Can you Solve it [duplicate]

----- + ----- + -----= 30 Use only (1,3,5,7,9,11,13,15)
14
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2answers
404 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 ($\div$).
6
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4answers
588 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
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0answers
71 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
440 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
228 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 ...
10
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4answers
377 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
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1answer
271 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
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1answer
322 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
254 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
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1answer
195 views

Fastest Way To 6 Pawns On the B To H Files

MASSIVE UPDATE: I decided to play around with this again today, and I found MAJOR improvmemts for the B to G file games. See if you can beat me! If not, give proof as to why my game is optimal (To ...
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 ...
13
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1answer
505 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 ?
4
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2answers
624 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
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1answer
407 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
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2answers
345 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
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1answer
665 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
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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
169 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? ...
31
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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?
38
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8answers
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
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3answers
675 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
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1answer
238 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 ...
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1answer
199 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?