Greatest Common Factor
The GCF of 16 and 40
8
Must be an even number ending in a 0,2,4,6 or 8.
2 Rule of Divisibility
The first 4 multiples of 5
5, 10, 15 and 20
List the factors for 6
1, 2, 3 and 6
Prime factorization of 36
36 = 2 x 2 x 3 x 3
The GCF of 12 and 8
4
The number must have a 0 in the ones place
10 Rule of Divisibility
The first 4 multiples of 20
20, 40, 60 and 80
List the factors of 12
1,2,3,4,6 and 12
Prime factorization of 52
The GCF of 6 and 13
1
The number must have a 0 or 5 in the ones place
5 Rule of Divisibility
The first 4 multiples of 6
6, 12, 18 and 24
List the factors of 24
1,2,3,4,6,8,12 and 24
Prime factorization of 24
24 = 2 x 2 x 2 x 3
The GCF of 21 and 49
7
Add the digits and the sum must be divisible by 9
9 Rule of Divisibility
The first 4 multiples of 13
13, 26, 39 and 52
List the factors of 37
1 and 37
Prime factorization of 100
100 = 2 x 2 x 5 x 5
The GCF of 72 and 90
The number must be divisible by both the 2 and 3 Rule
6 Rule of Divisibilty
The first 4 multiples of 18
18, 36, 54 and 72
List out the factors of 72
1,2,3,4,6,8,9,12,18,24,36 and 72.
Prime factorization of 67
67 = 1 x 67