Mathematics Stack Exchange
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Questions tagged [puzzle]

For questions about the mathematical principles behind puzzle, games, riddles, or their possible solutions. Questions that are not strictly mathematical in nature should be asked on Puzzling Stack Exchange.

Many puzzles, games, and riddles are based on mathematical concepts. This tag is for questions that ask about the mathematics behind a puzzle, game, or riddle, or about the solutions to mathematical puzzles.

If you already know the answer to the puzzle you are posting, you might consider posting your question on Puzzling Stack Exchange, instead. If you do end up posting your question on Mathematics Stack Exchange (MSE), please read the following meta posts on these kinds of questions before asking your question:

If you do end up posting on MSE, please make it clear in your question that you are "puzzling" the community and that you will be answer the question yourself if no one in the community posts your desired solution.

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Puzzle about subjects, classroom numbers and teachers who teach those subjects in classrooms

A,B,C,D,E are teachers who may teach: math, physics, chemistry, biology or geography(one subject per person, we don't know who teaches what). They teach in classrooms 110,111,112,113,114. Tell which teacher teaches which subject in which…
Yoda
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Puzzle about phographers in Africa taking pictures of 2 Animals which name corresponds to last name of their friends

Leo Lion, Tom Tiger, Eddie Elephant, George Gazelle, Peter Panther, Luke Leopard were on photographic safari in Africa. Every photographer took a picture of 2 animals. Every of these 2 animals belonged to spiecies corresponding to last names of…
Yoda
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A question from a job interview: math function that returns the number of positive numbers.

Describe a mathemathical function that receives 5 parameters, And returns the number of positive numbers. $f(x_1,x_2,x_3,x_4,x_5)\to 5,4,3,2,1,0$ - according to the number of positive numbers. Unfortunally i didn't have success on beating this one.…
StationaryTraveller
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Puzzle about total winnings in a card game

Mr. White is playing with Mr. Green. They decided that stake of every round will be 50% of total money that Mr. Green has. Mr. Green said that he has in total 32$. So in the first round stake was 16$. They played for 7 rounds and Mr. Green won 4 of…
Yoda
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Three friends problem.

Once there were 3 friends: A, B, and C. They went together to have a lunch at a hotel. The lunch they had cost \$60 according to the menu. To pay the bill, each one contributed \$20. But when the waiter brought the sum to the manager, the manager…
Ravindra Sahay
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Demystify / Solve a number progression.

I've worked on this for two days and haven't gotten anywhere. They don't seem to grow by an even percentage, nor by an incremented percentage, nor by a flat number increment. (as far as my limited math know-how goes) Can anyone figure it…
Helen
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What does this word represent?

What five digit number does serve represent if VCR+VCCT=SERVE? I have tried using 4,5,and 6 for C but that doesn't seem to work. Please help I do not understand.
user145574
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What is the legality of the following series?

What is the legality of the following series? 1,11,21,1211,111221,312211,132221,11133211,31231221,13111213112211,111331121113212221...
dmitriy
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Math Brain Teaser! Can't solve, please help!

The sum of face values of two coins is twice the difference of the two. Find them. My math professor gave us a brain teaser, but I am extremely confused on how to solve it. I am aware that it might be a April Fool's joke, but he still wants a…
user137980
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Coin weights game theory

http://blog.tanyakhovanova.com/?p=279 This is an extension of the problem posted here. You have 14 coins. You know that 7 are real, and 7 are counterfeit. The real coins are 1000g, and the fake coins are 999kg. You have a balance accurate enough…
Stewart
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Riddle: Minimum time to cross the bridge?

I've recently been asked to solve a riddle, which sounds something like that: There are 4 people on the one side of the bridge. They have only 1 flashlight. It takes respectively 1, 2, 5 and 10 minutes for those people to cross the bridge. Rules for…
Gintas K
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Finding affiliation of a number to a finite number of sets of incremental numbers

I have different sets of incremental numbers starting from zero like this: $S_1=\{0,1,2,3\}$ $S_2=\{4,5,6,7\}$ $S_3=\{8,9,10,11\}$ Each set has the same cardinality. I want to know, given a number $x$, the number of sets and the cardinality of the…
W4lker
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Maximum number of knights on a $2 \times n$ ($n\ge 2$) board

So, the puzzle is what is the maximum number of knights one can place on a $2 \times n$ ($n\ge 2$) board such that no two knights can attack each other. Apparently there is a formula for this $2\cdot\left(2\cdot(n/4) + \min(n\,\%\,4, 2)\right)$ How…
khirod
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When would the first collision occur on A Golden March

From A Golden March from the futility closet. Draw a circle whose circumference is the golden mean. Choose a point and label it 1, then move clockwise around the circle in steps of arc length 1, labeling the points 2, 3, and so on. At each step,…
yiyi
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Is negative 20 equal to negative 20? May be not!

Proof: Using simple Algebra it can be proved that -20 $\neq$ -20. Is it Algebraically correct, can I treat this as a puzzle only?
Avinesh
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