Divisibility Tests for 9 and 11: Interactive Demonstration with Digit Rules

This GeoGebra example interactively demonstrates the divisibility tests for 9 and 11 by using digit-based patterns and immediate feedback. It shows how to determine whether a given integer is divisible by 9 (via the digit-sum rule) or by 11 (via the alternating digit-sum/difference rule), turning the learning process into a cycle of “apply the rule → check → record results.” The core math concepts include number theory, congruence-style reasoning behind the divisibility rules, and the practical factor understanding often linked with MCM/MCD ideas. Construction-wise, it relies on Random and RandomElement to generate test numbers, If to branch into correct/incorrect判定 (divisible vs not divisible), and Polygon plus multiple labeled text objects (e.g., p1texto*, p2texto*) to present the rule steps and the outcome. It also tracks performance using variables like aciertos and fallos, and uses interface objects such as buttons and geometric/layout placeholders to structure the visualization. Suitable for middle/high school lessons on number theory, classroom demonstrations, and student practice or self-testing.