https://www.sinmath.com/topic/divisibility-rules/Recent content in Divisibility Rules on Mathematics Learning PortalHugo -- gohugo.io© {year} | Mathematics Learning PortalMon, 11 Aug 2025 15:17:22 +0700https://www.sinmath.com/theorem-of-multiples-of-3-rules-proof-and-examples/Mon, 11 Aug 2025 15:17:22 +0700https://www.sinmath.com/theorem-of-multiples-of-3-rules-proof-and-examples/Theorem of Multiples of 3: Rules, Proof, and Applications 1. Introduction The theorem of multiples of 3 is one of the quick division rules taught in elementary school and often used up to high school level. The rule is simple: A number is divisible by 3 if the sum of all its digits is divisible by 3. Although it seems like a quick trick, this rule actually has a strong mathematical basis, especially in the concept of modular arithmetic.