# Questions tagged [mathematics]

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

59 questions with no upvoted or accepted answers
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### What does this mathematical operator do?

The solution to this puzzle is one I came up with when working on this puzzle: What is the answer of this math puzzle? For two natural numbers a,b, can you figure ...
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...
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### Can we find four identically colored numbers?

Take the positive integers {1, 2, 3, ...} and color them red, green or blue. Is it true that no matter what coloring is chosen, we can always find three distinct numbers x, y and z so that x, y, z ...
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### The Snake and the Hunter

The Snake and the Hunter is a game for two players who play in two rounds interchanging the roles of snake and hunter. The game is played in a rectangular grid of points, say 6×6. In both rounds the ...
907 views

### Dissecting a figure into 2, 3, 4, and 5 parts but not 6

This figure is divided in 2, 3 and 4 equal parts of same size and shape, but it is not possible to do it in 5 equal parts of same size and shape. Is it possible to find a figure that can be divided ...
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### Powerful number systems

Imagine I have two positive integers, $a$ and $b$. Can you find the last digit of the sum $a+b$ given only the last digits of $a$ and $b$? More generally, can you find the last $n$ digits of $a+b$ ...
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### I'm a number with a special product, so name me when you think you've got it

In the blocks that come before, their special product tells us more. To guess my scheme you'll need calculation, but only little tests of recreation. Each block contains atoms strong as Thor, ...
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### A Glutton and a Split Check

N, T, A, B are arbitrary constants in this problem. I have only definitively solved the N=1 subproblem, so, if the general problem cannot be solved, I will be satisfied to mark as accepted a solution ...
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### Doubling the cube with rational Meccano strips

In three monographs published in 2006, 2008 and 2014 Gerard 't Hooft considered "Meccano mathematics": how to construct specified distances and regular polygons by a rigid system of ideal ...
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### Is it possible to create a knot that is locked only when the rope is stretched?

Is it possible to create a knot that is stable/locked when the rope is stretched? When the tension is relived the knot should open.
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### Can you construct a nonagon with 47 rods?

Stiv's Diabolical Instruments now offers a bundle of exactly 47 equal-length rods that can be joined by hinges at their ends – and only the ends – to form planar linkages (i.e. all hinge axes are ...
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### Connect dots on a grid with one continuous line (optimization)

(This question is the third puzzle of the Connect dots puzzle series. You can find the first two puzzles here and here, respectively. The original question and photos originate from webadventurer. ...
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### The smallest number

Some time ago I created a program to generate a table, and printed the first seven rows and columns. Somehow however I forgot to print the headers and the title of the table. I only remember that it ...
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### Ideas on spatial puzzles for a city walk

Background. With the relaxation of covid-related restrictions, there was a need for intelligent city walks. Walk here is a moving between city objects by a certain (deterministic/stochastic) route. I ...
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### The madness of a master

It was midnight. Mr. Holmes was suffering from abdominal pain, shortness of breath, pain in the bones, skin lesions and whatnot? So in this condition, why would Mr. Holmes drive to Brazilian Churches, ...
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### Formula for the sequence 1, 1, 1, 21, 3, 1, 4, 1, 5, 1, 6, ... if the 21 isn't a mistake

The sequence 1, 1, 1, 21, 3, 1, 4, 1, 5, 1, 6, ... appeared in one of my tutorial sheets in 2019. I assumed that the fourth term, 21, was a mistake (was supposed to be ..., 2, 1, ...) then it made ...
288 views

### Find a missing number in this 28x21 grid

355|066|677|855|677|081|044|855|355|062|216|677|216|855|224|044|034|046|051|677|355|264|044|046|044|351|886|043 043|044|886|357|886|352|225|357|043|222|993|001|233|968|046|225|062|041|351|886|043|227|...
156 views

### A math-based jigsaw

This is a fun puzzle I invented 50 years ago. ("Loops of Zen" is rather similar, idea-wise.) Here is a random solution (doesn't spoil much)... ...and here are the building blocks: Basic is ...
245 views

### Infected Cylinder and Torus

A variant of the well known Infected Checkerboard problem. If we've a 𝑛x𝑛 square, then we fold it along top and bottom row to form a cylinder. A cell in this cylinder becomes infected if at least ...
154 views

### Does anybody know the history of this star/triangle puzzle?

Does anybody know the history of the puzzle posted by Mario Bilotti? Who created this puzzle? Who deserves the credit? Find 10 triangles in a five pointed star using two straight lines
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### The Game of Numbers (#02)

Related to The Game of Numbers (#01) Agatha just decided it still isn't enough because she thinks it's way too easy. She decides to add one more rule to the list and change some of the existing rules. ...
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### Find Relation between the following numbers

If: $23×3=76$ $13×3=26$ $3×3=9$ $33×3=70$ Find $43×3=?$
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### Ernie and the conduits of constant cross-section

It all started last week, when Acme Engineering loaned him a prototype version of their 3D Home Printer (this was as a reward for Ernie providing them, patent-free, with a suitable building material - ...
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### Do puzzles like "write 120 using four 8" have a specific name?

Here on puzzling SE there is the category "calculation puzzle", but it's very broad. I'd like to know if somebody gave a specific name for such puzzles.
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### Three planes fuel tanks for less than halfway around the world - how can one plane make it around the world and what is the minimum fuel tank size?

Inspired by this recent question here is a variation. Three identical aeroplanes are based on an island with one airport. Each plane can take fuel to get less than halfway around the world. Fuel can ...
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### A robot moving on a grid. Part 2

This is an extension of the discussion A robot is placed on a grid point. At each move the robot must take three steps along the edge of the grid. After each step the robot must turn right. Lengths of ...
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### Code Breaking ( Sort of )

So someone sent me this code breaking/riddle to solve and I got really confused on it. I do need help on it, The Code needs to come out into a Phrase ( group of words ) CLUE 1: 2210232013400 - ...
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### ARG Puzzle Gate 15 Help

Me and my group (yes I'm in a group trying to solve this) are currently working on an ARG puzzle and we are stuck. The first image/clue to the entire puzzle is what is seen below. The creator of this ...
241 views

### Strategy for solving "Hypatian Enigma" puzzle (all lines add to 38)

The "Hypatian Enigma" puzzle consists of 19 hexagonal blocks numbered 1 through 19. The blocks are arranged in 5 rows. The first and last rows have 3 blocks, the second and fourth row has 4 ...
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### Can you assemble the icosahedron?

An icosahedron has 20 faces which are equilateral triangles. Tom wants to create a very hard mechanical puzzle. With his brand new 3D printer in mind he designs 20 puzzle pieces with identical shapes ...
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### The Puzzle Noob’s New Game

This is a generalized version of a TED-ED puzzle. You just wrote a very good puzzle on PSE, getting three upvotes a week. However, the puzzle noob hates your puzzles, and sends you to their dimension ...
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A deadlock is a position in which neither player has won and neither player has a legal placement available. My question is, "Can you find a deadlock position in Minefield?" And, if you ...
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### Can you find the missing letters?

A pattern of letters has had letters 10 through 20 deleted. Your job is to find out what letters should go in spots 10-20. Here is the pattern: a, b, c, d, d, d, f, e, f, _, _, _, _, _, _, _, _, _, _, ...
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### The Angel Problem - Sticker Devil Variation

So If you are aware of the angel problem, I propose a Variant: we introduce the Sticker Devil: A normal devil, with the added ability to sacrifice his turn to color any and all White Tiles that are ...
1 vote
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### What is the value of x? 16-48-98, 32-->x

What's the value of x? (Original picture) 4 | 8--8--1 16-48-98 | | 32--->x I have four possible answer choices: 130, 132, 160, and 260. I'm not sure which ...
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### Not a sudoku, but still fun?

Context: I was trying to solve some of the puzzles on this site, when it occurred to me to make a puzzle variant myself. I immediately could construct one with my additional rule. Making an ...
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### Searching online catalogs is a pain. Can you tell me if it's worth my trouble?

Searching online catalogs is a pain. Can you tell me if it's worth my trouble? As an example, I searched the following online catalog of a well-known country-wide British outlet for the keyword "...
1 vote
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### Decode this message to stop the destruction of Science!

An extremist religious organization called "The Redeemed Against Scientific Usurpation of God's Authority", or RASUGA, have converted the world's leading time travel researcher to their ...
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### Filling a sudoku/latin square like array

Let us build a square array in the following manner, which I would like to call a modified sudoku: 1) Every row and column contains only one copy of a positive entry and there are exactly $t$ such ...
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### 2 square overlap

A simple geometric math puzzle (too simple for MO). Seeing two overlapping square beermats, I had the idea: One mat is the other rotated by an angle. All colored areas are the same (say 1, arbitrary ...
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### what is the probability of winning in casino

A new casino has opened up in the town which has only one game. Now, we all know the house has an edge in casino. For this game the house has a win probability of 60%, and the player has a win ...
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### Secret message from a kitten (definitely not a cosmic horror from beyond time)

Can you decrypt this secret message?
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