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
4
votes
3 answers

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

Is there a way you can get the number $6$ from the numbers $6, 7, 8$, and $9$ using only addition, subtraction, multiplication, and division, without combining two numbers e.g. using the $6$ and $7$ to create $67$. You may use parentheses and you…
mgher
  • 71
4
votes
2 answers

Cost of Frying Oil

I'm struggling to put together a formula that would estimate the amount and cost of frying oil to fry, say, chicken. Let me define some variables: a - cost of oil per liter b - number of times the oil can be reused without compromising quality of…
MathNewbie
  • 235
4
votes
2 answers

Maximise pizza crust

You are baking a pizza but you love the crust and so want to maximise it. Is it better to bake a circle or a rectangular pizza - assume both must be the same thickness? There is no limitation on the shape of your baking tray. My guess is the…
user471851
  • 43
4
votes
3 answers

How to calculate what % faster $x$ is than $y$

I recently automated a process at work. The manual process took $16$ hours ($960$ minutes). The automated process only takes $7$ minutes. How do I calculate how many times faster the new process is? I'm hoping for a formula so that I can apply the…
SQL_Deadwood
  • 143
  • 1
  • 5
4
votes
2 answers

Find the sum of $ (1 \times 1!) + (2 \times 2!) + (3 \times 3!) + \cdots+ (50\times50!)$

What will be the sum of following series $$ (1 \times 1!) + (2 \times 2!) + (3 \times 3!) + \cdots+ (50\times50!)$$ Is there any general solution for $n$ terms? I have tried writing nth term and then summing up but I was unable to write the nth term…
geeky me
  • 373
4
votes
1 answer

Question about logic riddle (patch of lily pads that doubles every day)

I wasn't sure if the Math SE is the right SE to post this question, but after reading this question at the Meta SE, I think this SE is the right place. In a video on YouTube about logic riddles, one of the riddles is: In a lake, there is a patch…
Kevin
  • 980
4
votes
2 answers

The angle between two clock pointers

Fun with math time The other day a friend of mine asked me for this: What is the value of the angle between two clock pointer when it's 11:50? Of course the correct answer is not $60$ degrees, and it's quite clear why it's not. Indeed, aside the…
Enrico M.
  • 26,114
4
votes
3 answers

Lifting a toilet seat without breaking urine stream

Yes, I know the title is bizarre. I was urinating and forgot to lift the seat up. That made me wonder: assuming I maintain my current position, is it possible for the toilet seat (assume it is a closed, but otherwise freely deformable curve) to be…
user178156
4
votes
2 answers

How to find the formula for the sequence $1, 3, 6, 10, 15...$?

Before I say anything, I have to say that this isn't an advanced mathematics question; I'm just a $15$ year-old student, who came across a mathematical problem. I saw a picture displaying a "ingenious money saving method", that if everyday you put…
Takeshino
  • 43
  • 5
4
votes
1 answer

A recreational math problem, integers in a grid

I was thinking of the following recreational math problem: We have a $4\times 4$ square filled with integers $a_{1,1},...,a_{4,4}$. It has $30$ sub-squares $A_{i,j,k}$, corners of the form $a_{i,j},a_{i,j+k},a_{i+k,j}, a_{i+k,j+k}$, such that sum of…
student
  • 63
  • 4
4
votes
1 answer

Starting for Self Study of Mathematics

I am a Mathematics enthusiast but after High School i took a job. Now i want to do self study in mathematics and to dive deep into the subject. What should i do ? What books and articles should i read?
Renil Babu
  • 41
4
votes
0 answers

minimum number of times to change tyres.

I saw this brain teaser. Suppose, we travel 1000 miles on a tricycle and we have 5 tyres, then how many times do we need to stop to change tyres so that each of the tyres travelled the same distance? Here is a solution: After 400 miles change the…
Lost1
  • 7,895
4
votes
5 answers

Solving large multiplications in my head

What would be the best approach to solve 73 x 42 in my head? I started with 70 x 40 and then 3 x 40 and combined, but at this point I forgot what I had done and ended up getting lost and not figuring it out. Is there a good method for solving…
Jacob Raccuia
  • 185
4
votes
4 answers

Does other solutions exist for $29x+30y+31z = 366$?

I was asked this trick question: If $29x + 30y + 31z = 366$ then what is $x+y+z=?$ The answer is $12$ and it is said to be so because $29$ , $30$ and $31$ are respectively the number of days of months in a leap year. Therefore $x + y + z$ must be…
Aswin P J
  • 143
4
votes
4 answers

An interesting wire-tying problem to match wire ends in as few trips as possible

You have $N$ wires that all extend from one location to a second distant location. The wire ends at both locations are unlabeled, and the goal is to label them all (on both ends) with distinct labels $1,2,\ldots, N$ so that the two ends of the same…
user2566092
  • 26,142
1 2 3
…
35 36