# 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.

52 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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### 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 ...
861 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 ...
627 views

### Gold and silver coins in sealed envelopes

Alice has freely chosen to put either a gold coin or a silver coin in each of an infinite sequence of envelopes numbered 1,2,3,... Bob can open any number of envelopes and check the coins within, ...
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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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### 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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### 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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### What is a Good Pasta Number™?

This puzzle is inspired by JLee's What is a Word/Phrase™ series and the subsequent "Number" variants. (Actually, I'd originally tried to create a more original puzzle using the same idea, ...
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### Dishonest dungeon staff

You are faced with the difficult task to set up a dungeon for adventurers. However you made a deal with the guild: any adventurer brave enough to beat the dungeon and reach the treasure room will be ...
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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 ...
284 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|...
153 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 ...
242 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 ...
151 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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### 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 ...
1 vote
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### Diamond Rush: Back to... um

It is summer in the Pse School Of Logicians, and everyone studying there is dying for a break (they absolutely hate school, and can do anything to get out of it). And because the teachers there are ...
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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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1 vote
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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
156 views

### 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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### mathematical puzzle whose solution seems to contradict its own hypotheses

This youtube video shows a mathematical puzzle that had me quite baffled, and at the moment I seem to disagree with the solution that is proposed as unique. A leaf is torn from a paperback novel. The ...
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### Bisecting a 3D object into two equal volume objects - 2

Given the following 3D object and means of an unmarked ruler to draw lines on its surface define a straight cut that will split it into two objects with the same volume. Hint: It seems to have at ...
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### How Do You Prove That This Puzzle Is Physically Solvable?

https://www.reddit.com/r/BeAmazed/comments/fyt7x9/it_seems_to_be_impossible_but_it_gets_done/?ref=share&ref_source=link The goal of the puzzle is to remove the wooden stick from the jar by ...
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### Poem coding scientific constants

The following Vogon poem contains various mathematical, scientific and cosmological numbers. There are ten. Can you find them? Credit for partial solutions. A BTAUJV BTA ALEJM AV EUMJM FAV EATR O
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