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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Explaining to an alien on the phone which is our LEFT and our RIGHT.

I hope this question has some sort of meaningfulness. Suppose you are on the phone with an alien which is on his planet. For some reason he know which are our UP and DOWN and our FRONT and BACK. It's not difficult to explain him where is the UP or…
user3621272
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Finding out a person's age in days given their birthday dd/mm/yyyy?

It has to be somebody alive today. Assume that the day is today - September 15, 2014. This is convenient because the leap years will be regular (once every for years; the weird rule applies to $1900$ but not $2000$) If I am given somebody's birthday…
MT_
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A problem related to the number 1963

You are allowed to use +, -, / and * (plus, minus, division and multiplication) signs and bracketing. These signs you can put between the numbers 1963 to form mathematical expressions. You must put at least one sign between two numbers and – cannot…
Jaska
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Winning a card game

Scenario: Each player has a deck of N cards. The first player controls an object called Grindclock, which means that at each turn, he can either : Add a "charge" counter on Grindclock, or Remove the top X carts of his opponent's deck Only one of…
Nison Maël
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Alphametic-like fraction equaling 1/2; uniqueness of solutions

This problem is kind of like those alphametics puzzles. The challenge is to assign each whole number from 2 to 9 to the letters in $$\frac{10^3A+10^2B+10C+D}{10^4+10^3E+10^2F+10G+H}$$ such that the fraction equals $\frac{1}{2}$. (The original…
algorithmshark
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2 Trains and Fly Problem. Find the number of trips made by the fly back and forth.

Question: A Train A is approaching at a speed of 10m/sec, another Train B moving in the opposite direction at a speed of 20m/sec. A fly whose absolute speed is 50m/sec goes repeatedly from A to B and back, without loosing any time at any of the…
Abhishek Potnis
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In Towers of Hanoi (with 3 sticks and n disks without backtracking), do all legal sequences of moves reach the solution?

Updated Question : How to show that in TH we never reach a state where there are no paths to the solution? ( without reversing moves, as if reversing is allowed this becomes trivial ) Edit : Thanks to Stéphane Gimenez for pointing out the…
jimjim
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Guess the Polynomial

Player ONE has a finite degree polynomial $p$ with integer coefficients in mind whose domain is the reals. Player TWO gets to ask Player ONE to evaluate the polynomial at two points $x_0,x_1$ and Player ONE responds with $p(x_0)=y_0$, and…
Rustyn
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Calculating the number of triangles

I am trying to calculate how many triangles that can be found in an equilateral triangle with $2n$ lines starting at the bottom angles and ending at the opposite side, such that equally many lines start/end of either side. This is rather hard to…
JohnWO
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Don't understand this problem: There are only 2 pairs of positive integers $(x,y)$ for which...

..both $\frac{21}{x}$ and $\frac{70}{y}$ are in lowest terms and for which $\frac{21}{x} + \frac{70}{y}$ is an integer. One such pair is $(1,1)$. What is the other such pair? This is a Mathematics League problem. The answer sheet says, "...GCD of x…
Kat
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Find the values of $(a,b,c)$ such that $a^{2013}+b^{2013}=c^{2013}$ and $a^2+b^2=c^2$.

My professor likes to give our class some questions for fun every once in a while. He posed the following problem in class yesterday, and I've been stuck. Find the values of $(a,b,c)$ such that $a^{2013}+b^{2013}=c^{2013}$ and $a^2+b^2=c^2$. (The…
Sujaan Kunalan
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Numbers Brain Teaser

Alice and Bob have two positive integers, x and y respectively, glued to their foreheads, so that each can read the other’s number but not their own. They also know that |x − y| = 1. The following conversation is overheard between Alice and…
Jason Lindquist
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General and Simple Math Problem.

Three friends brought 3 pens together each 10 dollars. Next day they got 5 dollars cash back so they shared each 1 dollar and donated 2 dollars. Now the pen cost for each guy will be 9 dollars (\$10 -\$1). But if you add all 9+9+9 = 27 dollars and…
Jag
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How to greet a mathematician on his birthday with an excitement

Someone told me this, but I dont get it. $$\Gamma (Happy Birthday + 1)$$ Why is this the way to greet a mathematician on his birthday with an excitement?
Leo
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Creating a schedule for Beer Olympics I have coming up. I am struggling to create a schedule for 9 teams to play 6 games. HELP!

I am planning a “beer Olympics” for me and my friends and I need to write out a schedule. There are 9 teams (I know) and 6 games to play. In the past we have had 8 teams and this was much easier. I would like each team to play every other team at…
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