1. Rules for divisibility 2 + 1 Math Rocks! - YouTube
Divisibility Rules
Rules for divisibility Math Rocks! - YouTube

2. Summary of Divisibility Rules
Number
Divisibility Rules 10 5 2 3 9 6 4 8

3. Divisibility by 4 Multiply 10’s digit by 2
Add this product to 1’s digit
If the sum is divisible by 4 then so is the number
Example: 4696
9 x 2 = 18
= 24
If 24 is divisible by 4 then so is the original number

4. Divisibility by 8 Multiply 100’s digit by 4 Multiply 10’s digit by 2
Add product of above numbers to 1’s digit
If the sum is divisible by 8 then so is the number
Example:
7 x 4 = 28
2 x 2 = 4
= 32
If 32 is divisible by 8, then so is the original number

5. Common Multiples We need to sell 100 hot dogs! Buns come in packs of 8
Wieners come in packs of 12
What do we do?????????

6. Common Factors
What factors do the numbers 120 and 135 have in common?