1. Prime Factorization (Factor Trees) Greatest Common Factor
Prime Numbers
Composite Numbers
Factors
Prime Factorization (Factor Trees)
Multiples
Least Common Multiple
Greatest Common Factor
Divisibility Rules

2. Divisibilty Rules Number It is divisible if… 2 A number ends in
Examples Examples that
to support do not work. 2
A number ends in
0, 2, 4, 6, 8
10, 12, , 17, 79
36, 98 3
The sum of the digits is divisible by 3
3, 6, 12, , 17, 23 4
If the last two digits are divisible by 4 or the number ends in 00.
44, 100, , 77, 38
120, , 14 5
If the number ends in 5 or 0.
10, 25, 55, , 77, 88 6
If the number is divisible by 2 and 3.
6, 12, 24, , 44, 50 9
If the sum of the digits is divisible by 9.
9, 18, 189, , 980, 98 10
If the number ends in 0.
10, 20, 30, , 38, 88
Divisibilty Rules

3. Prime Numbers
A PRIME number is a number that has only two factors: 1 and itself.
Example:
2: only 1 and 2 will go into 2
3: only 1 and 3 will go into 3
5: only 1 and 5 will go into 5
Other prime numbers are :
7, 11, 13, 17, 19, 23, and many more!

4. Greatest common Factor (GCF)
To find the GCF do the following:
Step 1: List all the factors for each number
Step 2: Find the largest factor these two numbers have in common
Example:
Find the GCF for 60 and 72
60: 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60
72: 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, 72
The largest number 60 and 72 have in common is 12, therefore the GCF = 12

5. Least Common Multiple
To find the least common multiple do the following:
Step 1: List the multiples for each number
Step 2: Find the smallest number they have in common other than zero.
Example:
Find the LCM for 7 and 5
7: 0, 7, 14, 21, 28, 35, 42, …
5: 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, …

6. Quiz: Factors
List the factors each number. Then check your answer by clicking the “CHECK” button.
List the factors of 8:
List the factors of 10:
List the factors of 4:
List the factors of 20:
List the factors of 16:
List the factors of 25:
List the factors of 100:
List the factors of 3:
REVIEW
CHECK

7. Answers: Factor Quiz
List the factors each number. Then check your answer by clicking the “CHECK” button.
List the factors of 8: 1, 2, 4, 8
List the factors of 10: 1, 2, 5, 10
List the factors of 4: 1, 2, 4
List the factors of 20: 1, 2, 4, 5, 10, 20
List the factors of 16: 1, 2, 4, 8, 16
List the factors of 25: 1, 5, 25
List the factors of 100: 1, 2, 4, 5, 10, 20, 25, 50, 100
List the factors of 3: 1, 3
REVIEW
Back to Quiz

8. Composite Numbers
Composite numbers are numbers that have more than two factors.
Example:
4: 1, 2 and 4 go into 4
6: 1, 2 , 3 and 6 go into 6
8: 1, 2, 4, and 8 go into 8.

9. QUIZ
Factors
Factors are numbers that go into another number. To find the factors of a number, find the pairs.
Example:
Factors of 20
1 x 20
2 x 10
4 x 5
20: 1, 2, 4, 5, 10, 20
Then write them in order from least to greatest! Then write them in order from least to greatest!
Factors of 50:
1 x 50
2 x 25
5 x 5
50: 1, 2, 5, 25, 50
Remember: A factor will never be larger than the number itself.

10. Prime Factorization (Factor Trees)
QUIZ
Prime Factorization (Factor Trees)
Factor Trees are used to find the PRIME FACTORIZATION of a number. 70
Circle the number if
it is prime
Prime Factorization of 70 is: 2 x 5 x 7

11. Multiples are infinite,
QUIZ
Multiples
Multiples are all the numbers a number will go into. Multiples are infinite!
Examples:
Multiples of :
5: 0, 5, 10, 15, 20, …
3: 0, 3, 6, 9, 12, 15, 18, …
20: 0, 20, 40, 60, …
0 is the first multiple
of every number.
Multiples are infinite,
so you must end each
line with …
to show infinity.

12. Quiz: Prime Factorization
List the prime factorization for each number. Then check your answer by clicking the “CHECK” button. 72 50
100 90 20 15
CHECK
REVIEW

13. Answers: Prime Factorization Quiz
72: x
50: x
100: x
90: x x
20: x
15: x 3 2 2 2 2 2 2
Back To
The Quiz
REVIEW

14. Quiz: Multiples
List the multiples for each number. Then check your answer by clicking the “CHECK” button.
List the multiples of 8:
List the multiples of 10:
List the multiples of 4:
List the multiples of 20:
List the multiples of 16:
List the multiples of 25:
List the multiples of 100:
List the multiples of 3:
CHECK
REVIEW

15. Answers: Multiple Quiz
List the multiples of 8: 0, 8, 16, 24, 32, …
List the multiples of 10: 0, 10, 20, 30, 40,…
List the multiples of 4: 0, 4, 8, 12, 16, …
List the multiples of 20: 0, 20, 40, 60, 80, …
List the multiples of 16: 0, 16, 32, 48, 64, …
List the multiples of 25: 0, 25, 50, 75, 100, …
List the multiples of 100: 0, 100, 200, 300, 400, …
List the multiples of 3: 0, 3, 6, 9, 12, …
BACK TO THE QUIZ
REVIEW