Divisibility Rules
Number Theory Basics: Divisibility Rules
Divisibility Rules
Divisibility Rules
What you'll learn
- Fast divisibility tests for 2, 3, 4, 5, 6, 8, 9, 10, 11 — without doing long division.
- How to combine two rules (e.g. divisible by 12 = divisible by 3 AND by 4).
- Olympiad-style tricks: finding missing digits, counting how many numbers in a range satisfy a divisibility condition, and reasoning with LCM to find "smallest/largest number divisible by several numbers".
Key concepts
- Divisible by 2 — last digit is even (0,2,4,6,8).
- Divisible by 3 — sum of digits is a multiple of 3.
- Divisible by 4 — last two digits form a multiple of 4.
- Divisible by 5 — last digit is 0 or 5.
- Divisible by 6 — divisible by both 2 and 3.
- Divisible by 8 — last three digits form a multiple of 8.
- Divisible by 9 — sum of digits is a multiple of 9.
- Divisible by 10 — last digit is 0.
- Divisible by 11 — (sum of digits in odd positions from the right) − (sum in even positions) is a multiple of 11 (including 0).
Worked example
Is 4356 divisible by 12?
Step 1 — 12 = 3 × 4, so check divisibility by 3 AND by 4.
Step 2 — Digit sum of 4356 = 4+3+5+6 = 18, a multiple of 3. ✓
Step 3 — Last two digits are 56, and 56 ÷ 4 = 14, a whole number. ✓
Step 4 — Both conditions hold, so 4356 is divisible by 12 (4356 ÷ 12 = 363).
Common mistakes
- Forgetting that "divisible by 12" needs BOTH the 3-rule and the 4-rule, not just one.
- Misapplying the 11-rule by not alternating signs correctly on the digits.
- Assuming divisible-by-4 also means divisible-by-8 (it doesn't — always re-check the specific rule).
Quick check
- Which of 348, 522, 615 is divisible by 6?
- Find a digit to place in 7_35 so the number is divisible by 9.
- How many numbers from 1 to 100 are divisible by both 4 and 6?
Open the Practice tab for graded questions on Divisibility Rules.
Interactive Exploration Suggestions (Drishti Live Worlds)
- Use the platform-native live simulation (digit-rule checker / number grid highlighter) for this topic.
- Mirror / body / home activity: pick five house/shop numbers and test each against 3, 4, 6, 9, 11 rules; log results in a table.
- Voice or text reflection with AI Mentor: explain why the digit-sum trick for 3 and 9 works.
AI Mentor Prompts (Socratic, Board-Adaptive)
- "Explain this concept to a Class 6 student using one real example from an Indian home, school, market, or festival."
- "What is one common mistake students make here, and how would you catch yourself making it?"
- Stretch: "How does this connect to coding, robotics, money, health, environment, or a future career?"
Gamification, Portfolio & Parent Visibility
- Complete the core practice + one extension activity (photo, table, short reflection, or mini-project) for base XP + topic badge.
- 5-7 day streak or family discussion note = multiplier + visible artifact in parent/principal dashboard.
- Best real-world application stories (anonymised) featured on class or national leaderboard.
Robotics, STEM & Future Skills Bridges
- One hands-on project or measurement using the Drishti kit or household items that makes the concept physical.
- Direct link to at least one Future Skill track (Money Management, Green Tech, Cyber Defenders, Micro-Entrepreneurship, AI Mastery, Sustainable Living, Personality Development).
- Coding extension where relevant (simple script, simulation, or data logging).
NEP 2020 & Full Education OS Alignment
This material emphasises experiential "learning by doing", competency (apply/create/analyse), vocational exposure, critical thinking, and multidisciplinary connections. Designed to feed live worlds, AI Mentor (with memory), gamification, robotics, parent analytics, and future skills — not just exam prep.
Portfolio Evidence Idea: Your photo/table/reflection/project + one sentence on "How this helps me in real life or a possible future path."
Open the Practice tab for aligned questions (easy/medium/hard + case-based) with full AI scaffolding.
See curriculum for cross-links and the full future-skills/robotics chapters.
Key Takeaways (TL;DR)
- What you'll learn
- Key concepts
- Worked example
- Common mistakes
Master this topic with Drishti OS
Get unlimited mock tests, AI-powered mentorship, and complete video courses when you join.
Start Free Practice