Mathematics Stack Exchange
Mathematics Stack Exchange

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.

3301 questions
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riddle about friend of friend

let's say we live in a "very strange" world of Facebook, in which everyone has $1000$ friends. In addition, every $n$ people will have exactly $\lceil{1000 * (\frac{1}{10})^{n-1}}\rceil$ friends in common if $n \leq 3$, not more than a friend if $n$…
zfm
  • 300
2
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1 answer

Prove that it is impossible to make 18

Today, I was shown the following puzzle: Find a way to make the numbers $ 7 $ through $ 18 $ using any three adjacent numbers in the grid below: \begin{array} {|c|c|} \hline 10 & 10 & 9 \\ \hline 5 & 7 & 3 \\ \hline 8 & 11 & 11…
Joe the Person
  • 127
2
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1 answer

Conway's napkin puzzle

This puzzle is from the book "Mathematical Puzzles: a connoisseur's collection", and I am only asking for a part of it. 48 people are seated in a big circular table, where they find between each pair of settings, there is one napkin. As each person…
Xiaochuan
  • 1,542
2
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1 answer

Flip over every 2nd coin

Possible Duplicate: A tedious puzzle (but not homework) There was this question on a show called "Growing Pains Of a Teenage Genius" The question is as follows: 1000 coins are lined up, heads up oooooooooooooooooooooooooooooooooooo... and…
bobobobo
  • 9,502
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1 answer

Display Number as a sum so that sum of reciprocals of the summands is 1

Good Evening, Right now I am solving some Mathematic Puzzles and want to create a formula for the following: Display the Number 2008 as a sum of natural numbers so that the sum of the reciprocals of the summands is 1? You can use as many summands as…
CodeFanatic
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2 answers

How to create 3 squares from this arrangement of matches?

There's a matches riddle that I can't quite solve. Given the following layout (a 4 matches plus sign connected to a 8 matches square): __|__ __|__ | | |__ __| I need to transform this into exactly 3 squares by moving 5 matches only. It's…
Maayan
  • 23
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1 answer

What is the name of this puzzle?

Anyone knows what is the name of this puzzle:
user134115
  • 21
2
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1 answer

100 prisoners and a light bulb

I'm curious if there is a solution,however ineffective, for the puzzle when the prisoners do not know whether initially the bulb is on or off. Second, has several bulbs modification of the problem been studied? Where, if yes? There may be for…
user122424
  • 3,926
2
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2 answers

Minimum number of weighings necessary

8 boxes each having different weights are numbered from 1 to 8 (the lightest 1, the heaviest 8). The total weight of 4 boxes are equal to the other 4’s total, and your task is to identify these two groups. You have a balance scale with two pans on…
Taner
  • 247
2
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2 answers

Math Puzzle - Fishing

One day 3 men (Ed, Eddie and Eric) decided to go fishing. They agreed that everyone takes one third of the total number N of fish caught. After fishing they went to sleep. At 3:00 AM Ed woke up. He wanted to take his 1/3 and leave but he realized…
12YearsOld
  • 23
2
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5 answers

Stumped on an alphanumeric puzzle

My 5th grade daughter gave me this problem, and I am stumped! Each letter, $A,B,C,D,E$ or $F$ represents one of the digits, $1,2,3,4,5$ or $6$. You are given the following problem. $D \cdot BCEA=F8B0$. Solve for what each letter represents. Any…
Joe
  • 37
2
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1 answer

Numbers puzzle - Distribution of fruits

Question :- 38 fruits, apples, oranges, plums and guavas, are distributed among 4 people A, B, C and D. Each one gets a minimum of one fruits of each type and a maximum of four fruits of each type. There are 12 apples. There are two females, each of…
Fin27
  • 958
2
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4 answers

How to understand the analog clock problem?

I know the answer to this riddle: How often does the minute hand pass the hour hand on an analog clock? I know they pass 11 times every 12 hours, but I don't understand how to get to it, no matter how many resources I refer to. Does anyone have a…
Oleksiy
  • 145
2
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1 answer

Two truths and a lie

Saw this and I'm not even sure this is a valid question. It seems that A is a lie is true. But I can't wrap my head around the case in which B is a lie. So here it goes: Two truths and a lie: Which is a lie? A. This statement B. Not this…
Ruochan Liu
  • 344
2
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3 answers

Math riddle: What is the smallest positive possible outcome?

I spent hours trying to solve this riddle, I got $412-385=27$ as the smallest outcome, does anyone have a way to find the smallest positive outcome and prove it? The riddle: You have the digits $1, 2, 3, 4, 5, 8.$ You need to place them in these…
YahavB
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