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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Previous year like 2016

How can I find the previous year $y$ which was like 2016 in sense that January first is Friday, it has a leap year and date of Easters are the same on both years?
Curious
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Finding an $a$, such that $\forall x(x^x-a\cdot x!=0).$

I've been finding myself wondering about this equation for a long time, however due to my limited math knowledge, I can't solve or even determine if there is a solution to that equation. So I ask: is there an equation or number that can satisfy…
Henke
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Composite numbers which divide the concatenation of their prime factors in chaos order

Since numbers divide the concatenation of their prime factors in neat ascending/descending order are have been listed at OEIS (See https://oeis.org/A259047 and https://oeis.org/248915 ). Here we are only talking about composite numbers which divide…
Jim Stratowsky
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How to get the interest rate per quarter given the semiannual interest rate?

I have this economics problem. What is the present worth of $500.00$ Rupiah deposited at the end of every three months for $6$ years if the interest rate is $12\%$ compounded semiannually? According to the solution, the interest rate per quarter…
reeglysonforubuntu
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understanding how multiplying a number by itself and than using the result for division gives you a consistent result

hey guys i am basically a programmer and just came across a peice of mathematical calculation that i was curious to understand , have a look below :: 1200 / 40 * 40 = 1200 1200 / 30 * 30 = 1200 1200 / 20 * 20 = 1200 how come when you multiply a…
Alexander Solonik
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Arrange 1-12 around a circle

This is a very interesting word problem that I came across in an old textbook of mine. So I know its got something to do with plain old algebra, which yields the shortest, simplest proofs, but other than that, the textbook gave no hints really and…
user245665
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Rotation schedule for 6 persons and 2 locations

I like to make a rotation schedule for a dinner party where everyone is new, so the idea is that everyone gets a chance to meet as many new people as possible. Setup: I have 6 persons attending (lets name them A to F). I have 2 locations (tables)…
Paul
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Really easy percentage % question?

So I have an exam coming up. Just trying to calculate the bare minimum I need to pass (although I am aiming for much higher). I need 40% to pass the subject. So from a previous exam worth 30%, I already have 18% of my grade. I have an exam coming…
Flula
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Calculate total arc length of spherical cap of a specified circumference

For the past day, I have been trying to calculate the arc length of a sphere from a pole to a longitudinal cross-section with a specified circumference. I have diagrams and equations belo w. However, I am getting answers that seem incorrect. Are…
Christopher Rucinski
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What was the average speed for the whole journey?

Last weekend I went to London ... I calculated my average speed going to London was 30 mph On the return journey the traffic was terrible and I calculated an average speed of 20mph What was the average speed for the whole journey ?
paul
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Price Difference Question. Unable to derive 3rd equation

A man buys Rs.7 apples. When after a few days the price of the apple goes down by Rs.2, he buys 6 more apples. Both the amounts were in whole numbers, were two digits and has the same digits. Find how many apples could be bought for Rs.144. The…
ultimate
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Perception of time: 1 day to John is X days to Sally

I'm a ruby programmer writing a calculator for a fun blog post. I want to quantify the perception of time between two individuals. John has lived 236676.87 hours Sally has lived 438290.5 hours 1 day to John is 0.010140407890302081% of his life 1 day…
jBeas
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How can I know whether to round a quotient up or down (based on whether the number after the decimal point is 5+ or not) with ONLY this information?

Say I have a special calculator that, when it divides one number by another, it gives you the answer in the form of, "quotient r remainder." For example, if you divide 5 by 3, it tells you "1 remainder 2." I want to be able to take those 4 variables…
user3169700
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How to get maximum number 500 out of one variable

Im designing a website and I need to make a sum which will allow the result to be a maximum of 500. So the variable can be anything from '0' to 'a billion' and second number is 12. So just by basic math I would like to always get either 500 or less…
Youss
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Solving a reaction-diffusion problem using Separation of Variables

$$U_{t} - D U_{xx}= -kU$$ where BC: $U_{x}(0,t)=0$, $U_{x}(l,t)=0$ where $0 < x < l$, $t > 0$ IC: $U(x,0)=A + B cos \big(\frac{2πx}{l}\big)$ where $ 0
Max
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