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.
123 questions
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Two unique birthdates
My Dad loves math riddles.
He said to me, “You know your late Grandma and her first cousin were both born in the same year and on a Friday. Grandma Hannah Prime was several months older than her first ...
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Joining Numbers Together [closed]
puzzle from 2.191.149.204 — lv. easy
Numbers are cool. If you join two (or more) numbers together, you get another valid number. For example add 3,756 and 4,192 together. You get 37,564,192 which is ...
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Mock binaries and divisibility
Inspiration from my usual column at the SPIEGEL.
A mock binary $m$ is a decimal number with digits $0$ and $1$ only.
Find the smallest $m$ such that $p\mid m$ for $p\leq30$ (it gets uninteresting fast)...
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Same-size factorization
Just had the idea but no solution and am too lazy to write a computer program (a solution without is preferred, of course). About 10^8 loops (10!*factoring) should suffice:
c is a number consisting of ...
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Cubic numbers out of cubic numbers
Are there infinitely many perfect cubes, such as 216 and 512, which remain a positive cube after removing its first and last digits?
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connections with numbers II
You are given the following 4 by 4 grid of numbers. Create four groups of four numbers such that the numbers in each group share some common property.
This puzzle is a (hopefully harder) sequel to ...
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connections with numbers
Next puzzle
You are given the following 4 by 4 grid of numbers. Create four groups of four numbers such that the numbers in each group share some common property.
(The placement of numbers in the ...
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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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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 ...
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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
...
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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) ...
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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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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 ...
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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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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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