Questions tagged [number-property]
Puzzles that use number properties such as even and odd, multiples of numbers, part of a well-known sequence (i.e. Fibonacci) or theorem (Pythagorean relations) or others in part of the method to solve the question.
114 questions
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Packing of 1 through 2025 into square with coprime adjacencies
Is it possible to fill a 45 × 45 square with 1 to 2025 = 452 such that each pair of adjacent number is coprime?
I'm pretty sure that it is possible and can probably get a construction, but I don't see ...
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3
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2
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Numerical crossword puzzles
I am considering to create a mathematical puzzle in the form of a numerical crossword. What I mean by that is a puzzle similar to a normal crossword but with digits instead of letters that form ...
- 143
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1
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Can you compute the common connection?
Each group in this connect-wall shares a number having those properties.
Aliquot sum is a prime
Catalan
Digit sum is a cube
Exponent of isolated Mersenne prime
Fibonacci
Friendly
Hexagonal
Lucas
...
- 21.5k
2
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0
answers
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What is the next number according to some law? [duplicate]
Question is as follows:
8619 - 4.
1253 - 0
9273 - 1
6656 - 3
1086 - ?
What is the question mark? I tried summing the digits, checking number of 2's in prime factorization, but 2nd relation (1253 - 0) ...
- 121
15
votes
5
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Geometry Puzzle: Tangent Circles with Integer Radii
Take as a semi-related example a series of circles with radii 10, 9, 8, ..., 2, 1. Place the first (largest) circle in the center and subsequent circles around it, keeping tangency between subsequent ...
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2
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Making a 2n-digit number divisible by 9
Alice and Bob play the following game, taking turns. Alice starts and writes a digit from the set M={1, 2, 3, 4, 5, 6} at the blackboard.
Bob appends another digit from the set M until a 2n-digit ...
- 13.1k
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Getting The Numbers 33 Through 99 Only Using 2, 0, 2, and 4 [closed]
How do you get the numbers 33-99 by using the numbers 2,0,2,4
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4
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How to get the numbers from 50 - 100 with the numbers 2, 0, 2, 4
All I need is 56-59, 69, 73, 75- 77, 79, 86, 90-94, 99. I've done the rest but I would love to hear other solutions.
Rules:
Use any of the following operations: basic operations (+ - x /), to the ...
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votes
2
answers
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Make numbers 1 - 30 using the digits 2, 0, 2, 5
Try to make all numbers 1-30 using the digits 2, 0, 2, 5.
Rules:
Use all four digits exactly once.
Allowed operations: $+,−,×,÷,!
\text{ (factorial)}, !! \text{ (double factorial)}, !!! \text{ (...
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1
vote
1
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Relation Between The Year And The Day
Today is January 22, the 22nd day of the year 2024.
I chose today because 22 is my favorite number.
Now for the problem. Try to relate 22 to 2024 using math.
For example, 58 is related to 271 because ...
- 479
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votes
5
answers
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Make numbers 1 - 30 using the digits 2, 0, 2, 4
Try to make all numbers 1-30 using the digits 2, 0, 2, 4.
Rules:
Use all four digits exactly once.
Allowed operations: $+, -, \times, ÷, !$ (factorial), x^y (exponentiation), √ (square root).
...
- 137
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11
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How to solve 1 2 3 4 5 = 5 4 3 2 1 (insert five pluses to make it equal)? A thorough solution needed
I consider it an amazing though very challenging puzzle:
1 2 3 4 5 = 5 4 3 2 1
One must insert exactly five pluses (i.e. five addition signs) somewhere between those ten displayed figures in such way ...
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0
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1
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this puzzle is based
This message is a basic numeric substitution cipher. The key is the standard, regular alphabet in the correct order (ABC...XYZ).
Here is the message:
3 16 15 7 20 1 22 23 13 1 22 10 16 15 21 27 16 23 ...
- 610
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votes
0
answers
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Can you find the missing letters?
A pattern of letters has had letters 10 through 20 deleted. Your job is to find out what letters should go in spots 10-20. Here is the pattern:
a, b, c, d, d, d, f, e, f, _, _, _, _, _, _, _, _, _, _, ...
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2
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What do 84, 96 and 108 have in common?
There's a certain property that's shared between (as far as I know) infinite positive integers including 84, 96 and 108. Below are the first thousand numbers with this property; I added that many in ...
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