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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.

3301 questions
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Identify heavier ball in group of $14$

We have $14$ identical looking balls, one of them is heavier than the rest of $13$ (all the others weigh exactly the same), how many of weighings (minimum) to find the heavier one? And I want to know if there is mathematical formula for this…
Djarallah Brahim
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Logic Question Bus Timetable Frequency of Service [Error in Calculation]

I would like to ask about an answer to a logic question involving a bus service, shown below. So I observed the bus stop at STATION and realised if it runs from 07:59 to 20:59, exactly 13 hours at 10 minute intervals, I calculated how many times a…
vik1245
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How to solve these types of sum puzzles

I have a math puzzle book, and in the chapter I'm working in right now, there's is this type of question that gets asked in one form or another. An example of such a puzzle: How many darts are needed to score exactly 100? How could one go about…
Garth Marenghi
  • 1,115
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"American Billions" puzzle: Find a 10-digit number (no repeats), where the first $n$ digits give a number divisible by $n$, for all $n = 1,\ldots,9$

I have no idea why the problem is apparently called this but here it is. Using only the digits $0$, $1$, $2$, $\ldots$, $9$, find a ten-digit number such that the number up to the $n$-th digit is divisible by $n$, for all $n\in\{1,\ldots,9\}$. In…
user458984
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Why my answer for that math brain teaser is wrong

Task: A team of reapers/mowers got a task to reap two meadows; acreage of the first meadow was twice as big as the second one. The whole team spent half the day reaping the first meadow; For the second half of the same day, the team split into two…
user3529850
  • 113
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When will the DMV line be full?

The DMV is able to accommodate $P$ people in line in its office. Unfortunate souls come in this line at an Entrance rate $I$ and the DMV processes each of them at a rate $E$ both of which have some unit in the form…
Alex
  • 111
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For a m by n minesweeper board, what is the maximum number of mines can exist so that any puzzle with those mines is solveable without guessing?

When I play the game Minesweeper, I make the puzzle more difficult by increasing the amount of mines and still keep the board. Once I set the maximum number of mines for a 9x9 board, which is $67$, I realise that the chance to win is almost zero(!).…
Lê Đức Minh
  • 442
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Make $\$100$ by taking $\$1$, $\$5$, and $\$10$... but we can take only $21$ notes

I am weak in mathematics, but I need to know if this is possible. I will take $\$100$ from my friend, but he will give me only $21$ notes of $\$1$, $\$5$, $\$10$. I need to tell him the numbers of each notes that will make $100$ dollars.
Sudip
  • 11
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A coin-weighing puzzle with 80 coins

In 80 coins one coin is counterfeit. What is minimum number of  weighings to find out counterfeit coin? PS: The counterfeit coin can be heavy or lighter.
Devender
  • 43
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Triangle Puzzle

There are 12 different sticks in a bag of integral length. You pull out 3 sticks, and you CANNOT put them together to form a triangle. What are the shortest possible lengths of the 12 sticks? What is the shortest length of the longest stick? THIS IS…
H.T
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How to find out the average salary?

I heard that this one was given problem in some job interview. Is this possible to do? Three people wants to know what is their average salary but they don't want to tell their salary to others. How can they find out the average? I couldn't think…
Jaakko Seppälä
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operations puzzle

Obtain the number 1500 by using the operations $×, +, -, ÷$ on the numbers $1, 2, 3, 4, 5, 6, 7, 8, 9,$ in that order. Brackets are allowed, but you cannot join digits to form multi-digit numbers: for example, you may not write $1$ next to $2$ and…
Ahmed Amir
  • 1,013
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Guess Who is the apple thief ??

At the end of class, My mathematics teacher gave us an interesting problem Which is as follow: Out of six boys exactly two were known to have been stealing apples. Harry said:Charlie and George. Donald said:Tom and Charlie James said:Donald and…
Vidyanshu Mishra
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calculate 40 minutes using n ropes

Possible Duplicate: Proof of recursive formula for “fusible numbers” There are N ropes given and it is given that each ropes burn in 1 hour You have to calculate 40 minutes using these. How can I do that?? I made 45 minutes, but 40 is not made…
devsda
  • 113
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Apple puzzle math

A salesman had 25kg apple. For convenience, he put some apples in 3 types of boxes, boxes of 1kg, 3kg and 5kg. He has a total of 10 cases of various kinds. Can he put 25kg apple to fit into 10 boxes? I'm thinking about creating $x,y,z \in…
Vchau_VN
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