1. Divisibility Rules
Page 10 in textbook

2. What does it mean to be divisible?
A whole number is divisible by another number if the remainder is 0 when the first number is divided by the second.

3. Rule A whole number is divisible by 2:
if the ones digit is divisible by 2
A whole number is EVEN if it is divisible by 2 (even #s: 0, 2, 4, 6, 8)
Examples: 2, 4, 6, 8, 10, 12, …

4. Are these numbers divisible by 2?
2,320
3,135 78
11,292

5. Rule A whole number is divisible by 3:
if the sum of the digits is divisible by 3
Example: 3, 6, 9, 12, 15, 18, …

6. Are these numbers divisible by 3?80
8 + 0 = 8 Not divisible by 3!
489
14,980
18,321

7. Rule A whole number is divisible by 4:
If the number formed by the last two digits is divisible by 4.
Example: 4, 8, 12, …, 104, 112, …

8. Are these numbers divisible by 4?
605
look at the last 2 digits: 05  NOT divisible by 4! 80
9, 948
11, 292

9. Rule A whole number is divisible by 5: If the ones digit is a 0 or 5.
Example: 5, 10, 15, 20, 25, …

10. Are these numbers divisible by 5?45
look at the ones place: 5  YES it is divisible by 5!
631
385
459

11. Rule A whole number is divisible by 6:
If the number is divisible by BOTH 2 and 3.
Example: 6, 12, 18, 24, 30, …

12. Are these numbers divisible by 6?
126
Check for 2: ends in 6 which is divisible by 2
Check for 3: = 9 which is divisible by 3
So, YES it is divisible by 6 because it is divisible by both 2 AND 3!
684
2, 835
1, 114

13. Rule A whole number is divisible by 9:
If the sum of the digits is divisible by 9.
Example: 9, 18, 27, 36, 45, …

14. Are these numbers divisible by 9?60
6 + 0 = 6, So NO it is not divisible by 9
138
900
8, 505

15. Rule A whole number is divisible by 10: If the ones digit is 0.
Example: 10, 20, 30, 40, 50, …

16. Are these numbers divisible by 10?56
Look at the ones place  6, so NO!
220
32,360
654