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Two-by-two grids of integers: which number replaces the question mark? [closed]
Here is my own puzzle: two squares are filled with numbers, another square contains numbers and question mark.
Which integer number replaces the question mark and why?
The ? has to replaced with a ...
- 1,366
0
votes
1
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402
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An increasing decreasing sequence
In math, there are all kinds of sequences
1545, 1218, 1071, 921, 851, 832, 799, 793, 774, 745, ... is (the start of) such as sequence
What is the best number?
Note:
Even in math things change, so ...
CommunityBot
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20
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1
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16
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1
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There are no employees at the store. Why not?
Janice goes to the print shop, but is very confused. There are no employees, but there is a big poster hung on the wall that could explain this. Unfortunately, it's unintelligible.
The sign reads:
<...
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6
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347
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Can you finish my riddle dear? Or will the answer remain unclear?
In the shadows where secrets dwell,
A brilliant mind, a tale to tell.
From France he came, with wisdom deep,
In silent halls, his secrets keep.
His name obscured by time's cruel hand,
A method born in ...
58
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0
answers
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Unsolved Mysteries: D'Agapeyeff cipher
The D'Agapeyeff cipher is an as-yet unbroken cipher that appears in the first edition of "Codes and Ciphers", an elementary book on cryptography published by the cryptographer Alexander D'...
- 2,192
7
votes
2
answers
522
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Extracting a fair coin flip from a biased die, with a time limit
There is a well-studied problem (including in several posts on this site) which asks for an algorithm for simulating a fair coin flip (or die roll) with a biased coin/die. Much work has been done on ...
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1
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Riddle in Cheshire Crossing comic
Looking for an answer to this riddle. I don't know it.
This is from the comic Cheshire Crossing. It is written by Andy Weir who also wrote The Martian.
It is possible this riddle has a real solution, ...
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20
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7
answers
2k
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Dissect the figure into two congruent parts.
Dissect the figure into two congruent parts.
Clarifications:
Shape ABCD is a square.
Points A, B and E are collinear.
Circular arc AE has center C and radius marked with the arrow.
Attribution:
May/...
- 2,192
6
votes
4
answers
2k
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A Simple Self-Referential Test
You can play it online here: https://www.brainzilla.com/logic/self-referential-quiz/simple-srq-2/
Original PDF source: http://mrhonner.com/wp-content/uploads/2012/05/Simple-Self-Referential-Test-2....
2
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0
answers
203
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Jane Street INTRO Puzzle
On Jane Street's puzzle intro page:
WHY PUZZLES
What’s a company like Jane Street doing with a page about puzzles? The act of solving puzzles, though that might seem abstract, is intrinsic to the ...
- 10.9k
8
votes
2
answers
443
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Dividing a hexagon into 4 identical regions
Building on other questions here (9 or 5, 7 & 11), I would like to ask: can you divide a regular hexagon into 4 identical regions. Same shape & area, and not mirror images of one another? Or ...
- 16.3k
14
votes
1
answer
790
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A clockwise arrangement
Find what this puzzle is about and tell me what word is hidden below.
The letter sequences for each circle:
AUAIU, AIE, IA, EO
AIAIU, AUAIU, AIE, EII, EO, IA, AIAIU
AUAIU, EII, IA, AUAIU
IE, IO
IA, IE,...
- 21.7k
8
votes
1
answer
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Ducks and Penguins
Solve on Penpa+
Across
1. By God, the man's a bastard! (4)
3. Biden has stolen diamonds from POTUS preceding him? That's not allowed! (9)
8. It populates currently unoccupied population centre (4)
12. ...
- 9,365
5
votes
3
answers
457
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Make a Venn diagram with five triangles
A Venn diagram consists of a set of partially overlapping shapes on a plane, arranged in a particular way: for any particular labelling of each of the shapes as "inside" or "outside&...
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