Mathematics Stack Exchange
Mathematics Stack Exchange

Questions tagged [recreational-mathematics]

Mathematics done just for fun, often disjoint from typical school mathematics curriculum. Also see the [puzzle] and [contest-math] tags.

Recreational mathematics is a general term for mathematical problems studied for the sake of pure intellectual curiosity, or just for the enjoyment of thinking about mathematics, without necessarily having any practical application or expectation of deep theoretical results.

Recreational mathematics problems are often easy to understand even for people without an extensive mathematical education, even if the theory they lead to may turn out to be surprisingly deep. Thus, recreational mathematics can serve to attract the curiosity of non-mathematicians and to inspire them to develop their mathematical skills further.

Many typical recreational mathematics problems fall into the fields of discrete mathematics (combinatorics, elementary number theory, etc.), probability theory and geometry. Important contributors to recreational mathematics are Sam Loyd and Martin Gardner.

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The largest number that cannot be made using a combination of $5$ and $11$?

Using just the numbers $5$ and $11$, what is the largest number that can not be made? An example of a feasible combination: $5 \cdot 20 - 11 \cdot 9 = 1$. An example of an unfeasible number is 13 because it is not a multiple of 5 and it is smaller…
QRIUS2KNW
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Find the pattern - puzzle

I have recently encountered a reasoning question that I have solved half , but I can't solve one part of it. Question : \begin{align} 3 + 5 + 6 =&\; 151872 \\[1.3ex] 5 + 5 + 6 =&\; 253094 \\[1.3ex] 5 + 6 + 7 =&\; 303585 …
Gaurang Tandon
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Finding Grandma's Car - a word problem

This word problem came up in a lunchtime discussion with coworkers. None of us are professional mathematicians or teachers of math, and we weren't sure how to get the answer. The word problem goes like this: Grandma Q drove her car downtown to do…
SteveED
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What is $(\frac{d}{dx})^\frac{d}{dx}$?

How I got interested:- Yesterday I watched this new video from 3blue1brown. And I realized that we can use the formula - $\textstyle\displaystyle{e^x=\sum_{n=0}^{\infty}\frac{x^n}{n!}}$ to almost anything. We can define matrix powers, matrix to the…
Rounak Sarkar
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Stardew Valley Farm -- Recreational Math Problem

In the game Stardew Valley, farming is essential. In order to plant seeds, one must till the soil using a hoe. A golden hoe is an upgraded hoe that allows the player to till 1, 3, or 5 squares of dirt with 1 swing in front of the player. After the…
Bool
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Writing on a paper- portrait or landscape?

For one of my exams I am allowed a one-sided equation sheet on a regular piece of printer paper. This got me thinking. If I write in rows, that is, I start at the top right and write until I get to the end, and then continue doing that, is it more…
user650810
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On Obtaining Positions in 2048

2048 is played in a 4*4 space. At the start there are 2 tiles spawned. Move - a swipe followed by a new tile (either 2 or 4) spawning. Position - any configuration of the various tiles and blanks on the board. End Position - a position where no…
Xiangyu Chen
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67 67 67 : use 3, 67's use any way how to get 11222

I need to get 11222 using three 67 s (Sixty seven) We can use any operation in any maner 67 67 67 use 3, 67's use any way but to get 11222.
prasad
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Mersenne numbers in the Collatz Conjecture

I've noticed a fun little thing about the Mersenne numbers for the Collatz conjecture$$2^n-1$$is odd$$3*2^n-3+1$$$$3*2^n-2$$is even$$3*2^{n-1}-1$$is odd $$3^22^{n-1}-3+1$$$$3^22^{n-1}-2$$is even$$3^22^{n-2}-1$$$$...$$$$3^n-1$$ Has this been noticed…
Jacob Claassen
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A Very interesting door problem

My teacher asked me a question which is as follow: There are $1000$ doors numbered $1$ to $1000$, and there are $1000$ men numbered $1$ to $1000$. Firstly $1$ numbered man goes and open all the doors. Secondly $2$ numbered man goes and close the…
Atul Mishra
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Sets expressible as the image of exactly a countable number of functions.

When working with a curve $C\subset\mathbb{R}^2$ one often finds that although $C$ can't be parametrized as a function $y(x)$ from the $X-$axis, it does admit a parametrization $x(y)$ from the $Y-$axis. A recurrent example is the cusp…
user378947
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Five balls in a scale

Suppose that I have 5 balls with different weights. A scale tells me which one ball is heavier than another. I have to write down the the pairs of balls I use before I use the scale. Is it possible to write down at most nine pair of balls which…
mathboy
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What is a good approach to demonstrate solvability of this type of puzzle without use of brute-force?

I chanced upon this puzzle in this question on the Anime & Manga site, and, like the OP, tried to solve it without any success. Here is a representation of the puzzle: the blocks may only be moved forward or backward along their shorter sides, and…
Maroon
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Bitcoin math problem example

Disclaimer: I'm not a mathematician, if something is complicated, please use layman's terms. Thank you. I'm wondering about this bitcoin thing. I have heard that mining is using a computer to solve mathematical problems. I understand that there are…
mickers
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$Z_n \backslash \{0\}$ splits into octets

Let $n=8m+1, m\in\mathbb{N}$. Does the set of nonzero elements of $\mathbb{Z}_n$ split into disjoint octets of the form $8_k=\{\pm a_k,\pm b_k,\pm a_k\pm b_k\}$? The computer tells me it is possible if $n$ is not a multiple of 3, up to $n=113$.…
Empy2
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