Decoding Divisibility Rules for 3, 6, and 9

Section role: supports the section on decoding the rules of 3 and 9 while the teacher transitions students from hands-on sorting to formal mathematical theory. Slides: (1) Title — 'Decoding the Rules of 3 and 9'; (2) Quick Review — bullets: recap rules for 2 (even numbers), 5 (ends in 0 or 5), and 10 (ends in 0) discovered in the previous card sorting activity; (3) The Magic Sum Rule for 3 — bullets: add all digits together, check if the sum is in the 3-times table, concrete example using 123 (1+2+3=6); (4) The Combo Rule for 6 — bullets: must pass the test for 2 AND the test for 3, example of 54; (5) The Rule for 9 — bullets: sum of digits is a multiple of 9, example of 729; (6) Mental Math Challenge — bullets: spot the common mistake ('Does ending in 3 mean it is divisible by 3? NO!'), prompt for quick student answers. Closing slide: 'Ready for Detective Training?' — hands control back to the teacher for individual practice exercises.

Lara from Teachy