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Results tagged with puzzle
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user 2233
Recreational mathematics or puzzles with serious mathematical content. Note that math contest problems are generally considered off-topic.
5
votes
Accepted
Number of 5x5 matrix permutations without repetitions in rows or columns
The answer to Question 1 is yes. What you have described is called a Latin square. Two Latin squares are isotopic if one can be obtained from the other by permuting rows, columns, and permuting the n …
- 32.1k
3
votes
Math puzzles for dinner
Here's one that I like that I just heard a few days ago. Alice and Bob play the following game. Alice is randomly dealt 5 cards from an ordinary deck of cards. She is allowed to show Bob 4 of the 5 …
- 32.1k
7
votes
Accepted
Separating Heavier from the Lighter Balls
In the comments, Emil Jeřábek and Terry Tao have given an asymptotic lower bound of $4n / \log_2 n$.
For the upper bound, $2n$ is trivial, obtained by weighing each ball individually. Here is a so …
- 32.1k
15
votes
A function that is defined everywhere but has unknown values
What about the (diagonal) Ramsey Numbers, $k \to R(k,k)$? These are fairly natural to define but notoriously hard to compute. Indeed, only the first two Ramsey numbers $R(3,3)=6$ and $R(4,4)=18$ are …
- 32.1k
4
votes
Math puzzles for dinner
Puzzle: Determine a strategy for the princes so that they are guaranteed to be set free eventually. The strategy should never output a false positive. …
- 29.8k
8
votes
Math puzzles for dinner
You have 1000 bottles of wine. Exactly one of the bottles contains a deadly poison, but you don't know which one. The killing time of the poison varies from person to person, but death is imminent i …
- 32.1k