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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18
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2answers
1k views

Ernie and the Drill Test

I dropped in to Ernie's place a while back and he asked me to stay and help calibrate his new Drilling Device. It was an impressive looking machine consisting of a large raygun-like thing mounted on ...
6
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4answers
652 views

Lining Up Recruits

The good soldier Schweik had been ordered to line up a band of new recruits before their officer gave them a speech. The desired line sought to minimize the average difference in height of adjacent ...
5
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1answer
770 views

Fit numbers on a grid with required sums for squares

Can anyone solve this puzzle or give me some tips? Rules: you have to use all 1, 2, 3, 4, 5, 6, 7 numbers in every 8 straight and vertical lines(4 vertical line and 4 straight line) And the summation ...
4
votes
1answer
544 views

Check to see if a Configuration is Possible: prove there's an Hamiltonian path on a connected subset of the square grid graph

Alright, here's a new one for you guys. Instead of solving it, you need to determine if any given configuration is possible to solve, without actually solving it. It needs to be a general method of ...
10
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1answer
871 views

An international affair: Find the common property in incorrect equations

Chaos at the international conference for world leaders: What should have been a peaceful exchange of ideas for common growth quickly exploded into hostility shortly after the German speaker addressed ...
1
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5answers
904 views

I Eight Two Much

If four 2s make eight, and three 2s also make eight, how many 2s do you need to make three eights, when you only have less than eight 2s?
3
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7answers
2k views

How many faces does this object have? [closed]

The object came with a few clues to help you figure it out. I can be viewed on paper I cannot be viewed in reality by your kind I am made up of what your mind can truly comprehend I resemble ...
8
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1answer
2k views

Can you pass through the ancient tomb? Find the correct interpretation for the symbols

You have been crossing this hot and wet place for weeks now, but when you enter the cool and mouldy ruin, you know in seconds it has been worth it. Nobody has ever been here ( - well nobody in last ...
3
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2answers
4k views

How to Determine a Magic Constant in a Magic Square?

A magic square consists of the numbers $1,2,\ldots,m^2$ placed into $m\times m$ square grid, so that every row, column, and both diagonals have the same sum. The magic constant of the square is this ...
4
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2answers
745 views

How can we compute the 6 missing numbers?

There are 3 datatables. We forgot the numbers around the third square. How can we compute the 6 missing numbers?(there are question marks instead of them)
16
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3answers
3k views

A library with less information than one of its books

How can a library contain less information than one of the books in it? The library is intended to be a set of books on shelves. The information content is the least number of bits to describe the ...
9
votes
2answers
543 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 < ... &...
10
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5answers
2k views

What's the Maximum Moves Needed for this kind of Puzzle?

Imagine a 4x4 square with a picture you need to make with tiles in it, now imagine you can swap any 2 pieces next to eachother (horizontal, and vertical, not diagonal.) What's the maximum amount of ...
10
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5answers
1k views

Ernie and the Mystery of Madame Mu

Quite a few years ago (I can't remember the date but it was obviously some time after I first met Ernie at a New Years Eve party in 2001) I got an unexpected phone call late one afternoon. It was ...
12
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4answers
1k views

Random Walk on Ring City

Ring City has 100 houses arranged in a circle. Alice starts at her own house, and every day she randomly moves to one of the two adjacent houses, each with 50% probability. She repeats this until she ...
6
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1answer
2k views

What is the number 4.9292683…?

Guess the next digits of this number. Where does it came from? 4.9292683
8
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1answer
443 views

What is the meaning of a “tetrad twist” in Thistlethwaite's algorithm?

I am having difficulty understanding the third stage of Thistlethwaite's algorithm. I am using http://www.jaapsch.net/puzzles/thistle.htm. The third stage has a factor of [8!/(4!4!)]2 *2*3. This ...
3
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2answers
443 views

Nerd on the Loose II - WHERE & HOW

Preface. Here is an relatively easy one, as compared to the previous part. We already found out when, let's find out where. Background. Professor Swannie Taco is a genius in most fields of science ...
9
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4answers
932 views

Generalized Path Guards

Suppose you are traveling and come to a fork in the road. One of them leads to something good like a cat shelter and a company handing out free ice cream and money, while the other leads to something ...
2
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3answers
2k views

One to Nine Puzzle

I got those from a cereal box. You can use each number 1 to 9 only once. Operation should match the value in the green box horizonal and vertical My problem is Operation Order isnt specify in the ...
8
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2answers
337 views

Place the numbers

Consider the set of positive integers. Each integer can be definitively placed either above the line or below it. Given the initial collection of placements below, what are The next two numbers in ...
7
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4answers
936 views

Nerd on the Loose I - WHEN

Chat. I've created a chat room in case anyone wish to discuss this further. Preface. This is the first time I'm creating a puzzle. Since I find enjoyment in science and technology, the series of ...
17
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1answer
3k views

The Laziest Surveyor

The new land surveyor and his boss arrived at the work site, a huge and perfectly flat parking lot. His boss said, "Your first assignment is going to be a tough one. You see this parking lot? It ...
4
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1answer
495 views

The Security to the Party [Part 29]

A party is being held at a local mansion. The host is very rich and his success is because of one thing — his famous recipe for Spaghetti! The only guests that may attend are people who correctly ...
4
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3answers
556 views

The Security to the Party [Part 20] [closed]

A party is being held at a local mansion. The host is very rich and his success is because of one thing — his famous recipe for Spaghetti! The only guests that may attend are people who correctly ...
11
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4answers
1k views

Optimization of area

You have a closed cord of length 100 meters which touches point $P$. There is a line $L$ whose closest point is 20 meters from point $P$. The value of a layout of cord is defined by the area ...
18
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2answers
2k views

1 in, 1 out (The Security to the Party Maze)

A party is being held at a local mansion. The host is very rich and his success is because of one thing ~ his famous recipe for spaghetti! The spaghetti recipe is kept in a secret room inside the ...
8
votes
1answer
436 views

The Security to the Afterparty

So, you got through the guards and to the party? Easy stuff! The number sequences were silly and you walked in and out multiple times. Now what? One of the guests you mingled with at the party has ...
6
votes
5answers
964 views

Travelling Light

I'm off hiking and I need to buy a bus ticket to the mountains. The ticket costs £4.25 and I have the following coins in my pocket: 2 x £2, 4 x £1, 50p, 3 x 20p, 2 x 5p, 2p, 7 x 1p Weight is ...
6
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6answers
2k views

4 balls - red and blue

I have a black box that contains 4 balls. 3 are red and 1 is blue. I remove two from the box without seeing them. I look at one of them, it is red. What is the probability that the other one is ...
2
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2answers
850 views

100 sequential parking spaces

I just came up across this question in the mathematics stack exchange site and found it quite interesting: 100 autonomous robotic vehicles enter a warehouse in random order to park. Inside the ...
1
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1answer
380 views

The Security To The Party (Part 19: Oh God Another One)

Oh God Another Recap A party is being held at a local mansion. The host is very rich and his success is because of one thing — his famous recipe for Spaghetti! The only guests that may attend are ...
10
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2answers
1k views

Ernie and the Orthogonal Network

I dropped in on Ernie a while ago and he told me that there was "good news and bad news". I asked him to tell me about it and he explained as follows: "Remember my Casimir-effect electric motor and ...
35
votes
1answer
4k views

Ernie's automatic parking valet

I was helping Ernie out in his shed a while back, when his favorite screwdriver suddenly wore out. I offered to go and pick up a new one for him and Ernie thought it was a great opportunity to test-...
2
votes
7answers
969 views

The Security to the Party [Part 9]

A party is being held at a local mansion. The host is very rich and his success is because of one thing ~ his famous recipe for Spaghetti! The only guests that may attend are people the host knows ...
9
votes
5answers
1k views

Will The Ant Ever Reach The Car [Part 2]

A car starts distance 1 from a wall then drives away at constant acceleration $c$. There is length of elastic tied between the wall and the car. Remarkably, this doesn't affect the motion of the car (...
2
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2answers
509 views

What can't I buy?

A certain chain store sells chocolate bars in packets of 17 and 9 only. Clearly, you could not get 8 or 25 bars. Find all quantities of bars that you cannot buy.
1
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4answers
747 views

What could have been the sentences I was thinking about?

I have just thought about an interesting problem in classical propositional logic to propose at this site, but lost my notes... I do recall, however, that the problem involved a particular contingent ...
6
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1answer
300 views

Balancing Weights

Source: Australian Mathematical Society Gazette Puzzle Corner 35 There are some weights on the two sides of a balance scale. The mass of each weight is an integer number of grams, but no two ...
4
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3answers
904 views

The generous team puzzle

An intelligent team, ‘Smarty Pants’, applying to a competition completes an evaluation form early. Since they are feeling generous they randomly spread their assignment to all 10 teams applying from ...
0
votes
1answer
392 views

Determine the largest even positive integer [closed]

Determine the largest even positive integer that cannot be written as the sum of two odd composite positive integers.
5
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4answers
3k views

Are you Really Smart

The government has introduced a standardised test to identify dumb people and make them ineligible to apply for any government jobs, a pass in the exam is mandatory for applications in future. It ...
5
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3answers
945 views

Crack the Code #3

You return to the bench after cracking the last code, and you notice an envelope on the ground directly under it. You put down your envelope with the previous code and pick up the new one, ...
7
votes
2answers
2k views

Can you help the traveller

A traveller decided to explore a square desert. He started from a point on the edge to point B, travelling perpendicular to the edge of the desert he started on. On reaching B, he then decided to take ...
2
votes
3answers
702 views

4 Doors and a Half Value prize

You're on a game show, playing for 1 million dollars! You've made it to the final round, there are 4 doors, you pick a random door (obviously, there's a 1/4 chance for all of them, let's say you ...
4
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2answers
992 views

Another 6 tries to guess a number between 1-100

Inspired by 6 Tries to Guess a Number Between 1-100, how many guesses would it take if you can ask if the outcome of an operation is equal, less than, or more than a number. In other words, Alice ...
6
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1answer
1k views

Non-Negative integers in to three groups

The non-negative integers are divided into three groups as follows: A = {0,3,6,8,9...}, B = {1,4,7,11,14...}, c={2,5,10,13...} Explain ? I have no idea how to proceed.
9
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2answers
1k 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 ...
3
votes
5answers
944 views

A belt, a stone and a wooden stick

We're on the middle of the most devastating war the Earth has gone through all its history. You and your brother in arms are in a plane that has been taken down while crossing the enemies lines. You ...
0
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3answers
910 views

Inheritance by cards [duplicate]

An old farmer passes away in his sleep. After a suitable period of mourning, his three sons find their father's will in his study. Amongst other, simpler bequests is the following: "I wish my small ...