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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1answer
62 views

Neighbouring numbers summing to a prime on a 4x4

Can you place every number from 1 to 16 on a 4x4 grid such that every pair of neighbouring (horizontally and vertically) numbers sum to a prime? Note that the generated primes can be reused. A ...
4
votes
3answers
453 views

Neighbouring numbers summing to a prime on a 3x3

Can you place distinct numbers from 0 to 9 on a 3x3 grid such that every pair of neighbouring (horizontally and vertically) numbers sum to a prime? Can you find multiple solutions? Note that the ...
-2
votes
1answer
86 views

Distance between two friends [closed]

Two friends are 200 meters apart in a concourse. They then both walk 100 meters each with their faces towards to each other. Yet after this 100 meter walk they are still 200 meters apart.
5
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4answers
359 views

What's wrong with this D20?

Here's a D20 I produced by 3D printing and finishing. Something is wrong with it relative to the intended design. What is wrong and how did it get to be that way? Hint:
4
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1answer
114 views

“Short” And Sweet Math

In the following chess diagram, how many possible chess postions exist? No looking at the solution! Source: P1359129 & Andrew Jonathan Mestel, Retros mailing list, 2/1/2019
10
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1answer
251 views

What is a Commutative Word™?

This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles. If a word conforms to a special rule, I call it a Commutative Word™. Use ...
98
votes
8answers
6k views

Make all the statements true

Can you make all the below statements true with a single click? If yes, explain how. Three + Eleven = Ten Seven + Five = Six Two + Four = Eight NB: 'A Single Click' means, with only a single left ...
4
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1answer
151 views

Find the least expense?

You want to build a shop between three roads in the shape of an equilateral triangle. What would be the best location for the shop so that you can reach each road with the minimum transportation ...
1
vote
1answer
88 views

One-digit products in a row of numbers, base-N

Generalizing One-digit products in a row of numbers to base-N: For which bases N does there exist at least one solution to the following: "The digits from 1 to N can be arranged in a row, such that ...
7
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4answers
2k views

Smallest number containing the first 11 primes as sub-strings

113257 contains the first 6 primes as sub-strings when reading them from left to right: 2: 113257 3: 113257 5: 113257 7: 113257 11: 113257 13: 113257 What is the smallest number that contains ...
7
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5answers
387 views

Patient No. 141

I have a rare disease and it is really dangerous. I need oxygen tanks supplying oxygen to me. It is like I rely on oxygen tanks more than water and food. I think that my path to cure takes ...
3
votes
1answer
138 views

The best way to hire people

“We get a lot of applicants for our job vacancies,” said Lionel. He waved a hand in the general direction of the call-centre. “Here at Open to Everybody Insurance Services the jobs don’t need much ...
12
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2answers
729 views

One-digit products in a row of numbers

The digits from 1 to 9 can be arranged in a row, such that any two neighbouring digits in this row is the product of two one-digit numbers. Arrangement: Is it possible to do such an arrangement ...
-3
votes
2answers
96 views

How do you make 29 only using the numbers 1 2 3 4 [closed]

How do you make 29 with only using the numbers 1 2 3 4? I have tried a lot of solutions and please remember that you can't use the number 5
44
votes
10answers
146k views

1 2 3 4 5 6 7 8 9 = 100

The sequence of numbers $1\ 2\ 3\ 4\ 5\ 6\ 7\ 8\ 9$ has the property that you can insert mathematical operators in between the numbers from $1$ to $9$ and make the expression evaluate to 100. For ...
9
votes
3answers
1k views

Painting a 4x6 grid with 2 colours

Can you paint a 4x6 grid with 2 colours such that it doesn't contain any rectangles whose corners are all the same colour? Can you do it without a computer? Rectangles must be 2x2 or greater and ...
5
votes
3answers
266 views

Painting a 10x10 grid with 3 colours

Can you paint a 10x10 grid with 3 colours such that it doesn't contain any rectangles whose corners are all the same colour? Rectangles must be 2x2 or greater and parallel to the grid's sides. ...
-3
votes
2answers
239 views

Next number in the sequence?

What is the next number in this sequence? 0, 6, 12, 19, 27, 35, 45, 54, 63, ? Good luck! HINT:
23
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11answers
10k views

The 100 soldier problem

I saw this problem many years ago. I am sure many puzzlers will know its original name. I was reminded of it when reading about Conquering of Regions problem. A Strategy Game Involving Conquering of ...
10
votes
2answers
584 views

A Magic Flying Saucer

Place 19 different positive integers on the vertices of this graph so that the 13 products of three numbers in a straight line are all equal. Do so in such a way that the product is as small as ...
8
votes
2answers
804 views

Can multiple wall timers turn lights on or off when required?

Imagine we have some simple mechanical 24 hour wall timers like this: There’s one restriction though, they’re badly designed so each one can only turn on once and turn off once in a 24 hour period (...
8
votes
1answer
502 views

Three lines through a square

Is it possible to draw 3 straight lines through a square such that they divide it into 7 equal-sized regions?
8
votes
1answer
748 views

Venn diagram with 7 equal regions

Can you draw 3 overlapping circles (Venn diagram) such that all 7 of the formed regions have the same area? For the case of two circles and 3 equal regions I found this answer: https://math....
4
votes
2answers
88 views

Pentagon with sides, diagonals and area that are distinct integers

Can you find a convex pentagon (5 sides) such that all its sides, diagonals and area are distinct integers? Note that a polygon is convex if all its internal angles are smaller than 180 degrees. A ...
7
votes
2answers
390 views

Quadrilateral with sides, diagonals and area that are distinct integers

Can you find a convex quadrilateral such that all its sides, diagonals and area are distinct integers? Note that a polygon is convex if all its internal angles are smaller than 180 degrees. Good luck!...
11
votes
2answers
2k views

Three knights searching for a princess in a castle

There is a castle with rooms arranged in a 4x4 square grid. The princess living in the castle sleeps in a different room each night, but always one adjacent to the one in which she slept on the ...
4
votes
1answer
144 views

Area of the square

Can you find the area of the following square given the known lengths? Good luck!
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1answer
148 views

How do I make numbers 0-100 using only the numbers 2, 0, 0, 4 in order? [closed]

Please help me I need to find out how to do this with maths.
4
votes
1answer
310 views

Two knights searching for a princess in a castle

There is a castle with rooms arranged in a 3x3 square grid. The princess living in the castle sleeps in a different room each night, but always one adjacent to the one in which she slept on the ...
32
votes
18answers
11k views

Use 2, 0, 1 and 8 to make 109

Assemble a formula using the numbers $2$, $0$, $1$, and $8$ in any order that equals 109. You may use the operations $x + y$, $x - y$, $x \times y$, $x \div y$, $x!$, $\sqrt{x}$, $\sqrt[\leftroot{-2}\...
62
votes
24answers
20k views

Make 0 0 0 0 = 8

Can you find a way to make: $0\ 0 \ 0 \ 0 = 8$ by adding any operations or symbols? You can use only these symbols: $+,\ -,\ *,\ !,\ /,\ \hat\, ,\ ()$. It is limited to this list, and ...
3
votes
1answer
66 views

Arranging people to be in a group with every other person at least once

There are 12 people. These people start in 4 groups - each with 3 people. They swap groups 4 times, so they are in a total of 5 groups. Is it possible for each person to be in a group with every other ...
6
votes
2answers
257 views

Do number sentiments work?

We are of a family of eleven When we join or depart numbers less than a cent Excepting those special ten We turn odd to even and even to odd Like a tiny miracle of god However, in general our company ...
1
vote
1answer
265 views

Math puzzle with logic programming

I had below question in one of my assignments for Login Programming for Artificial Intelligence topic. Solve the alphametic:     $ ABCDE $ $+$ $ CFGH$   --------...
4
votes
2answers
342 views

Find the ages of $3$ children based on information given and constraints

A man has $3$ children. Their ages are $a,b,$ and $c$. The constraints are that the ages add up to some value d and multiply to some value e such that $de=756$. Also, no child is more than $3$ times ...
10
votes
3answers
2k views

Othello - Most number of legal moves in a given turn

I asked this over on boardgames SE, and was directed to post here in hopes of getting an answer. Original post is here: https://boardgames.stackexchange.com/questions/29824/othello-most-number-of-...
-1
votes
1answer
157 views

Fated to earn money [closed]

Here's a puzzle I made. Joe has investments in Company A, Company B, and Company C. Joe is fated to earn $25.00 from Company A within 2 days from now. Joe is fated to earn $45.00 from Company B ...
9
votes
3answers
736 views

The Royal Mint of Alphagonia

In the Kingdom of Alphagonia nothing can be bought for less than 30 alphas, the local currency. 1) What three denominations of coins should the kingdom mint so that as many as possible of the (...
4
votes
2answers
221 views

Sum constrained number route grid

Take a blank 6x6 grid (2-dimensional matrix). Pick a cell to start, and write the number 1 in that cell. Then move to an adjacent cell horizontally or vertically. Write 2 in that cell. Continue to ...
4
votes
3answers
589 views

Trying to get to 1234567 with three levers of different function

I am trying to get 1234567. There are three levers, lever a, lever b, and lever c. Lever a shifts 1234567 to the right. So it would look like 2345671. Lever b swaps the third and fifth number. So it ...
3
votes
7answers
1k views

Yet another calculator problem [closed]

This is an easy one, just came out of my mind yesterday, while discussing calculator's architecture with a friend, even if it is not related to architecture itself. A man walks into his office. He ...
7
votes
1answer
544 views

4 identical shapes that touch each other?

It is known that one can have 4 shapes in a plane all touching each other, and not 5. You can add requirements to the 4 shape problem: Can you do it with 4 equal triangles? (No) Can you do it with 4 ...
13
votes
8answers
2k views

Matchstick Puzzles

Puzzle #1: There is a matchstick: | Add 2 more matchsticks to make the number, 11. Puzzle #2: There is a palace made out of 11 matchsticks: Move 2 matchsticks to make 11 squares. Puzzle #3: ...
7
votes
2answers
925 views

Big number puzzle

I saw this on rec.puzzles many years ago, but can't find the reference to credit the source. I am thinking of a large number. If you want to multiply it by a two digit number $ab$ with $a \lt b$, ...
-6
votes
2answers
267 views

Simple maths, that simple? [closed]

A simple maths question: 42 + 75 = 165 60 + 64 = 174 70 + 74 = ? That simple?
0
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1answer
263 views

Magic Race between Rabbit and Turtle - who will win?

The race is for 500km and these are the following items they can use in the magic race... Every defect will activate again after completing the mentioned time. Rabbit has the following items ...
10
votes
2answers
535 views

National Graph Lottery

In UK's National Lottery players choose 6 different whole numbers in the range 1 to 59, and win a large prize if all six match with the day's draw. Each choice of six numbers by a player gives rise ...
2
votes
1answer
144 views

What is a Dial Word™?

This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles. If a word conforms to a special rule, I call it a Dial Word™. Use the ...
5
votes
0answers
223 views

Which is the missing number?

I am working on this puzzle since last week. 01 ?? 05 12 10 13 15 09 14 02 08 03 04 07 11 06 which is the missing number ?? note : answer is not 16
9
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3answers
305 views

Know your primes

Did you know that a prime, regardless of its base, is always a prime? I am looking for a prime. It’s the largest of its kind. In solving this puzzle, the answer you may find. ...