Puzzling Stack Exchange Community Digest

Top new questions this week:

The FBI needs your help with this Zodiac killer message

During a recent thorough cleanup round at the main building of the San Fransisco Chronicle, an employee found a piece of paper stuck behind an archive closet in one of the many archive rooms. Her ...

knowledge cipher  
user avatar asked by sarsaparilla Score of 23
user avatar answered by codewarrior0 Score of 20

Mishustin's circle problem

This problem was given to high school students by the Russian prime minister Mishustin. We have a circle. We are given some point on the circle and its diameter, as shown below. We are given a ...

mathematics geometry construction  
user avatar asked by Dmitry Kamenetsky Score of 19
user avatar answered by Bass Score of 24

A number sequence in disguise

What number should replace the question mark? Explain why. ...

lateral-thinking number-sequence  
user avatar asked by Prim3numbah Score of 17
user avatar answered by codewarrior0 Score of 15

Which parent should you start playing against?

Let $k < n$, $k$ even, $n$ odd. Mary is to play $n$ chess games against her parents, alternating between her father and mother. To receive her allowance she must win $k$ games in a row. Given the ...

mathematics game-theory  
user avatar asked by Simd Score of 17
user avatar answered by Nuclear Hoagie Score of 14

Missing photograph

Which person's photograph should be pasted upright (NOT UPSIDE DOWN) in the blank space?

knowledge enigmatic-puzzle visual  
user avatar asked by chandanr777 Score of 15
user avatar answered by Stiv Score of 17

Relatively prime numbers

Can you fill in the circles with numbers such that: Each pair of circles connected by one line contains relatively prime numbers Each pair of circles connected by two lines do not contain relatively ...

mathematics logical-deduction calculation-puzzle number-theory primes  
user avatar asked by godlification Score of 13
user avatar answered by tehtmi Score of 14

PSE Advent Calendar 2023 (Day 2): Wall I want for Christmas

This puzzle is part of the Puzzling Stack Exchange Advent Calendar 2023. The accepted answer to this question will be awarded a bounty worth 50 reputation.< Previous Door Next Door > Resolve the ...

knowledge pattern seasonal connect-wall connections-puzzle  
user avatar asked by Stiv Score of 12
user avatar answered by sean47 Score of 13

Greatest hits from previous weeks:

Are there published Sudoku puzzles that require guessing?

I believe in a number of books I have read and solved myself, the introduction stated that guessing should never be necessary for any of the puzzles in the book. Instead, a handful of techniques ...

user avatar asked by demongolem Score of 57
user avatar answered by Donald.McLean Score of 10

Two doors with two guards - one lies, one tells the truth

You are a prisoner in a room with 2 doors and 2 guards. One of the doors will guide you to freedom and behind the other is a hangman–you don't know which is which, but the guards do know. One of the ...

logical-deduction liars  
user avatar asked by Rafe Score of 129
user avatar answered by Kevin Score of 55

6 Tries to Guess a Number Between 1-100

After every time you guess, you're told if you're right, too high, or too low. Is there a strategy you can use to guarantee you'll get it on your 6th attempt (or lower)? I know a strategy to get it ...

user avatar asked by warspyking Score of 20
user avatar answered by d'alar'cop Score of 33

10 digit number where first n digits are divisible by n

What is the complete set of 10-digit numbers using each value ($0$-$9$) once, such that the first $n$ digits form a number divisible by $n$ (for $n \in \{1,2,...,10\}$)? E.g. if the number were $...

user avatar asked by frodoskywalker Score of 16
user avatar answered by r3mainer Score of 21

A seven letter word - the meaning doesn't change if you remove letters

I am a seven letter word. If you remove one letter from me my meaning does not change. If you remove two letters from me my meaning still does not change, and if you remove three letters from me, my ...

riddle word lateral-thinking language  
user avatar asked by skv Score of 69
user avatar answered by warspyking Score of 109

If A cents can be paid with B coins then prove that B dollars can be paid with A coins

Looking for an intuitive solution to the following problem: In a certain country the following coins are in circulation: 1 cent, 2 cents, 5 cents, 10 cents, 20 cents, 50 cents, and 1 dollar. It is ...

mathematics logical-deduction  
user avatar asked by Hemant Agarwal Score of 27
user avatar answered by David McKee Score of 15

2 vs. 1.005^200

Without using a calculator or a computer can you determine which of these two numbers is bigger: $2$ or $1.005^{200}$ ? I saw this puzzle in a YouTube video, which I will post later.

mathematics no-computers  
user avatar asked by Dmitry Kamenetsky Score of 32
user avatar answered by ACB Score of 63

Can you answer these questions?

College Athletes

This puzzle is part of the Monthly Topic Challenge #16: Restricted Title: xkcd 2000-2500. Solve the following 10 sub-puzzles, then use the information you've found to solve the metapuzzle: Puzzle 1 ...

knowledge enigmatic-puzzle visual rebus sports  
user avatar asked by juicifer Score of 5

The newcomers' maze

I just joined Puzzling Stack Exchange, and the moderators decided to put me through a test to validate my account. They brought me to an unknown island, where lies nothing but a maze: I managed to ...

enigmatic-puzzle mazes  
user avatar asked by Jujustum Score of 2
user avatar answered by Rand al'Thor Score of 0

Decode the ancient prophecy

A team of archaeologists has discovered an ancient clay tablet. They understand the script it is written in, and have transliterated it to the Latin alphabet, but they do not understand the language. ...

enigmatic-puzzle cipher  
user avatar asked by Someone Score of 2
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