Exploring Prime and Composite Numbers with the Sieve of Eratosthenes

What is a prime number?

• A number with more than two factors

• A number with exactly two factors: 1 and itself

• A number that is divisible by 2

• A number that is less than 1

Which of the following is a composite number?

• 2

• 3

• 5

• 4

Who invented the method known as the Sieve of Eratosthenes?

• Pythagoras

• Archimedes

• Euclid

• Eratosthenes

What is the purpose of the Sieve of Eratosthenes?

• To find odd numbers

• To find composite numbers

• To find prime numbers

• To find even numbers

What is the first step in using the Sieve of Eratosthenes?

• Circle the number 1

• Shade in all multiples of 2

• Cross out or shade in the number 1

• Circle the number 2

Why is the number 2 unique among prime numbers?

• It is the only odd prime number

• It has more than two factors

• It is the only even prime number

• It is the largest prime number

What should you do after circling the number 3 in the Sieve of Eratosthenes?

• Circle the number 5

• Shade in all multiples of 3

• Circle the number 4

• Shade in all multiples of 2

Which multiples should be shaded after circling the number 5?

• Multiples of 5

• Multiples of 2

• Multiples of 3

• Multiples of 7

What are the factors of the number 7?

• 1 and 9

• 1 and 7

• 1 and 5

• 1 and 3

How many prime numbers are there less than 100?

• 20

• 25

• 10

• 15