Grade 5/Factoring
Divisibility by 3 (1148)
Determine if a number is divisible by 3.
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Quick Tip
A number is divisible by 3 if the sum of its digits is divisible by 3.
Teacher Resources
Teaching Notes
Teach the 'sum of digits' trick. It's magical for students.
Vocabulary
Divisible: Can be divided with no remainder.
Sum: The result of adding numbers.
Common Mistakes
- Looking at the last digit only
- Confusing with divisibility by 2 or 5.
- Incorrectly summing the digits.
- Not checking if the *sum* is divisible by 3.
- Applying rule to single digits incorrectly.
Differentiation
SupportProvide a list of multiples of 3.
ChallengeTry 3-digit numbers like 123.
Discussion Questions
- Why does the sum of digits rule work?
- How does the sum of digits rule work?
- Why is this rule useful for larger numbers?
- Can a number be divisible by 3 and 5? Give an example.
- How does divisibility relate to multiples?
Extension Activities
- Find the largest 2-digit number divisible by 3.
Parent Tip
Have your child add the digits of numbers you see daily.
Learning Path
Skill Cluster
Number Sense & Operations
Estimated Time
10 minutes
Skills Practiced
divisibility 3
Prerequisites
- 1147
- Addition of whole numbers
- Multiplication facts
Next Steps
- Divisibility by 6
- Divisibility by 9
- Prime and composite numbers
- Divisibility by 2
- Divisibility by 5
- Multiples of numbers