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.

5128 questions
0
votes
3 answers

Problem - Sum of digits

For every numbers with $3$ digits you calculate the product of the numbers. After that you take the sum of the products, what number do you get? I didn't know how to do this exactly. What would be the easiest way?
Ylyk Coitus
  • 970
  • 2
  • 10
  • 18
0
votes
2 answers

Understanding the following two equations

I'm reading through some texts and came across the following two lines. I'm curious how they should be read. Volume = $4/3\enspace π r^3$ Surface Area = $4\enspace π r^2$ In the example of Volume: Is $4$ divided by $3$, multiplied by $\pi$? Is it…
David Metcalfe
  • 187
0
votes
1 answer

Calculating my improvement via daily compounding

If I improve at something 1% daily what will be my overall improvement after 1 year? What is the formula to calculate this?
Dercni
  • 111
0
votes
4 answers

How to get 5 from the numbers {6, 7, 8, 9} using only addition, subtraction, division, and multiplication.

Is there a way you can get the number 5 from the numbers 6, 7, 8, and 9 using only addition, subtraction, multiplacation, and division, without combining two numbers e.g. using the 6 and 7 to create 67. Exponents, factorials, and trig functions are…
mgher
  • 71
0
votes
0 answers

Mathematical card tricks

For quite some time I have taken interest in analyzing card tricks that make use of a deep knowledge of advanced mathematics and there's been some progress. However, all the tricks I've tried decoding seem to be based on elementary math which any…
user65201
  • 1
0
votes
1 answer

Formula to calculate percentage withdrawal that will yield same value as principle decreases.

So I created this retirement calculator here http://www.abrandao.com/retire And the idea is if you save enough you can so when you withdraw say 4% you don't eat too much into your savings. But based on my calculation 4% of 500000 is $20k but next…
user265505
  • 101
  • 1
0
votes
1 answer

Generations paradox

I have $2$ parents, $4$ grandparents, $8$ great grandparents, etc. So, going back $N$ generations, I have $2^N$ great...great grandparents. But $2^N$ is seriously divergent. I only have to go back a small number of generations to exceed the total…
Pythagorus
  • 591
0
votes
1 answer

Find the odd one out

I've been trying to work this for a while and I believe the odd one is the 4th figure, but don't seem to find a satisfying justification for this. Any help? Few observations: 1) Bottom two dots seem to toggle left and right together. 2) Top items…
AgentS
  • 12,195
0
votes
1 answer

Determining the values for an array within limits

So I did some math on a function to produce positions within an array of which I wanted to record data. My initial math looked like this: $$ (n * \frac{100}{n})-1$$ This would allow me to determine the upper limit of the array, and then I could…
addohm
  • 105
0
votes
1 answer

In a set we have $a(b+c)=ab+c$. What is it?

suppose $A\subseteq \mathbb{N}$ and for any $a,b,c\in A$ with $a
user59671
0
votes
1 answer

What type of mathematics is this problem? (Scheduling maybe? I don't know what to search for to find help.)

Sample Problem: A well can supply 50 laborers per day. 40 laborers can build a new well in five days, up to 10 total. Each laborer can complete 1 stone per day. The new temple needs 5000 stones. *** What is the most efficient way to get to 5000…
Alix Sunder
  • 11
0
votes
1 answer

Formula that predicts the location of moving enemy

A rocket that explodes not on impact, but explodes on a timer will be shot from myself to the enemy. The timer can only be inputted at the start of the shot. The rocket can only go straight and has a speed of 1500m/s . The enemy is moving away from…
Gwapo
  • 7
0
votes
1 answer

Finding a future year in a cycle of years

I have a problem of finding a future year based upon a fixed past year. I can come to the correct answer if I use an if statement, but I feel this should be accomplished with one formula. For example, let $$\text{CurrentYear} = 2018,\quad…
Jim
  • 111
0
votes
3 answers

Rules of Roman Numerals

I've been working on a problem that involves discovering valid methods of expressing natural numbers as Roman Numerals, and I came across a few oddities in the numbering system. For example, the number 5 could be most succinctly expressed as…
Rushabh Mehta
  • 13,663
0
votes
0 answers

Circular track - finding distances between the bus stops.

Tried different combinations with simultaneous equations, but could not get the answer. Any easier way to get the answer. this is my workout.
Dinesh Potluru
  • 235
1 2 3
…
35 36