Number Theory

Is 5 prime or composite?

• prime, because it has two factors

• composite, because it has three factors

• neither

Is 21 prime or composite?

• prime, because is has 2 factors

• composite, because it has 4 factors

• neither

Is 49 prime or composite?

• prime, because it only has 2 factors

• composite, because it has 3 factors

• composite, because it has 4 factors

What is a composite number?

• a number with ONLY TWO factors

• a number with LESS THAN TWO factors

• a number with MORE THAN TWO factors

• a number with ONLY ONE factor

Which list has ONLY prime numbers?

• 1, 2, 3

• 2, 3, 5

• 2, 3, 4

• 2, 4, 6

List ALL the factors of 12

• 1, 2, 3, 4, 6, 12
• 1, 2, 4, 12
• 1, 12
• 1, 2, 3, 4, 5, 6, 12

What are the factors of 25?

• 1, 2, 3, 5, 10, 15, 25
• 1, 5,  25
• 1, 25
• 1, 5

GCF of 20 and 80

• 10

• 20

• 5

• 40

GCF of 9 and 36

• 3

• 6

• 9

• 12

GCF of 15 and 45

• 3

• 15

• 5

• 30