Lesson Description
This lesson introduces divisibility rules for numbers 2 through 10, helping students quickly identify factors, multiples, and simplify calculations.
Learning Objectives
- Understand and apply divisibility rules for numbers 2–10.
- Identify factors and multiples using these rules.
- Use divisibility rules to simplify calculations and problem-solving.
Topics Covered
- Divisibility by 2, 3, 4, 5, 6, 8, 9, 10
- Recognizing factors and multiples
- Applying rules to solve problems
Key Terms
- Divisible: A number is divisible by another if division results in a whole number.
- Factor: A number that divides another number exactly.
- Multiple: A number obtained by multiplying a given number by an integer.
Lesson Examples
Example 1: Divisibility by 3
- Add the digits of the number (e.g., 123 → 1+2+3=6).
- Check if the sum is divisible by 3.
- If yes, the number is divisible by 3; 123 ÷ 3 = 41.
Example 2: Divisibility by 5
- Check the last digit of the number.
- If the last digit is 0 or 5, the number is divisible by 5.
- Example: 85 ends with 5 → divisible by 5 → 85 ÷ 5 = 17.
Practice Problems
- Determine if 246 is divisible by 2, 3, 5, and 9.
- Check if 175 is divisible by 2, 5, and 10.
- Find factors of 36 using divisibility rules.
- Is 81 divisible by 3, 6, and 9?
Tips & Common Mistakes
- Always check the last digit for divisibility by 2, 5, or 10.
- For divisibility by 3 or 9, sum all digits carefully.
- Don't confuse divisibility rules; practice multiple examples to remember.
Summary
Divisibility rules are shortcuts that allow quick identification of factors and multiples. Mastering these rules improves calculation efficiency and prepares students for factoring, GCF, LCM, and problem-solving in Pre-Algebra.
Challenge Problems
- Find all numbers between 50 and 100 divisible by 4 and 6.
- Determine whether 2345 is divisible by 2, 3, 5, 6, or 9.
- Create your own number and explain which divisibility rules apply and why.