Newest Questions
29,692 questions
7
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1
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8
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Numbers which are the product of two numbers that share no digits
Say a positive integer is cute if it can be written as the product of two other integers greater than 1 that share none of their digits.
a) Find 12 consecutive integers all of which are cute.
b) Are ...
2
votes
1
answer
368
views
A Cypher I Created: U+74 U+48 U+65 U+20 U+72 U+65 U+61 ...
This is a compound cypher meaning it is several cypher methods inside of each other.
U+74 U+48 U+65 U+20 U+72 U+65 U+61 U+70 U+65 U+72 U+20 U+69 U+73 U+20 U+43 U+4F U+6D U+69 U+4E U+67 U+20 U+61 U+4E ...
4
votes
1
answer
273
views
The sum of divisors of current year is also the current year
We already knew that the current year is sum of first 9 perfect cubes and there is another hidden interesting fact.
But there is another twist: The sum of divisors of current year is also the current ...
- 1,935
5
votes
1
answer
462
views
Second-lightest coin from 30 with a 5-way balance
The following problem is lightly adapted from AoPS.
You have 30 coins of identical appearance but distinct weights. You have only a balance that can rank exactly 5 coins from lightest to heaviest. ...
- 10.5k
28
votes
2
answers
802
views
2-Dimensional Music
I've been listening to 1-dimensional music for most of my life. You know, the flat kind that only moves forward in time.
Only recently did I discover 2-dimensional music!
It really adds depth to the ...
- 8,066
2
votes
1
answer
128
views
6
votes
4
answers
684
views
Action / Counter-action riddle
The word is action
Its anagram - counter-action (to the action)
This is my own.
Additional details (added 11/12/25):
These actions belong to a political process.
Each word is both a noun and a verb.
...
- 1,049
-1
votes
0
answers
249
views
Do solutions exist for 3D tiling with Pentaminos/Pentacubes?
To make a long story short, I have developed an IOS App running the classic game with Pentaminos and Pentacubes (see my profile for details). I am now considering the tiling option game with the same ...
- 119
13
votes
1
answer
768
views
It's a seven letter word
It started with an argument
And ended with a fight
With a weapon no less
All over this tiny little thing?
- 10.2k
8
votes
4
answers
1k
views
Find the missing digits in 1/2024
1/2024 is equal to $0.000\overline{a9407114b245059c88d375}$.
Can you find the values of a, b, c, and d without using a calculator?
Long division is trivial. Can you use other ways to find the missing ...
- 1,935
0
votes
1
answer
162
views
Knights, Knaves and Spies, unclear solution provided
Puzzle
You are on an island inhabited by three types of people: those who only tell the truth (knights), those who only tell
lies (knaves), and those who sometimes tell the truth and sometimes tell ...
- 111
7
votes
1
answer
611
views
The first time in over a millennium
From Enigma — the big book of brain-teasers and games of logic (2008), Fabrice Mazza, Sylvain Lhullier, p. 54:
Prediction
Nostradamus proclaimed:
“On Wednesday, the 2nd of February 2000, a global ...
- 1,328
12
votes
4
answers
770
views
Heptagons trompe-l'œil ?
Seven outer blue, equal sized, regular heptagons touch the sides of a given, also equal sized, inner blue regular heptagon.
The green triangle has black vertices: the south and the, up to one, most ...
- 3,026