Grade 4/Factoring
Divisibility by 9 (1151)
Determine if a number is divisible by 9.
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Quick Tip
A number is divisible by 9 if the sum of its digits is divisible by 9.
Teacher Resources
Teaching Notes
Similar to the rule for 3. Sum of digits must be 9, 18, 27, etc.
Vocabulary
Divisible: Can be divided by a number without a remainder.
Multiple: The result of multiplying a number by an integer.
Common Mistakes
- Confusing with rule for 3
- Miscalculating the sum of digits
- Confusing with divisibility by 3
- Forgetting to check the sum of digits
- Incorrectly applying the rule
Differentiation
SupportList multiples of 9.
ChallengeIs 999 divisible by 9?
Discussion Questions
- If a number is divisible by 9, is it also divisible by 3?
- How does summing digits help determine divisibility by 9?
- What other numbers use digit sums for divisibility?
- Can you create a three-digit number divisible by 9?
Extension Activities
- Find a number divisible by 9 but not 10.
Parent Tip
Ask your child to check if numbers on grocery receipts are divisible by 9.
Learning Path
Skill Cluster
Number Sense
Estimated Time
10 minutes
Skills Practiced
divisibility 9
Prerequisites
- 1148
- Basic Multiplication Facts
- Addition of Whole Numbers
- Understanding Multiples
Next Steps
- Divisibility by Other Numbers
- Finding Factors
- Simplifying Fractions
- Divisibility by 3
- Finding Multiples
- Identifying Factors