
How do you know a number is divisible by 5?
Divisibility Rules: How to test if a number is divisible by 2,3,4,5,6,8,9
or 10. Divisibility Calculator

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Source: www.mathwarehouse.com/arithmetic/numbers/divisibilityrulesandtests.php
Divisibility rule  Wikipedia, the free encyclopedia

** Divisibility rule **
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See also: Parity (mathematics)
A *divisibility rule* is a shorthand way of determining whether a given
number is divisible by a fixed divisor without performing the division,
usually by examining its digits. Although there are divisibility tests for
numbers in any radix, or base, and they are all different, this article
presents rules and examples only for decimal, or base 10, numbers.
*Contents*
· 1 Divisibility rules for numbers 1â30
· 2 Stepbystep examples
· 2.1 Divisibility by 2
· 2.2 Divisibility by 3 or 9
· 2.3 Divisibility by 4
· 2.4 Divisibility by 5
· 2.5 Divisibility by 6
· 2.6 Divisibility by 7
· 2.7 Divisibility by 13
· 3 Beyond 30
· 3.1 Composite divisors
· 3.2 Prime divisors
· 3.3 Notable examples
· 4 Generalized divisibility rule
· 5 Proofs
· 5.1 Proof using basic algebra
· 5.2 Proof using modular arithmetic
· 6 Notes
· 7
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