Teaching students about the Sieve of Eratosthenes can help them understand how prime numbers work. Many students may watch a teacher of video clip about how to create a sieve but are unable to do it on their own. I've created several Moodle cloze questions that can help students try it out on their own and get immediate feedback. The image at the right shows what the sieve question looks like.
The student needs to simply select either prime or not prime for each questions. The fast way to do this is press p or n followed by tab to go the next question.

The second set of questions ask the student to identify whether a number is prime or composite.
There are seven different importable files (Moodle XML format) that contain prime and composite numbers.

• Prime and composite numbers from 2 through 20
• Prime and composite numbers from 2 through 50
• Prime numbers from 2 through 1,000
• Prime numbers from 2 through 10,000
• Composite numbers from 2 through 1,000
• Composite numbers from 2 through 10,000

The larger sets are broken into separate prime and composite files so that you can import them into separate groups allowing you to determine how many prime and composite numbers a student is exposed to in a particular activity.

There are three ways to try out this activity.
Login to the free Math Activities at Moodle.Aschool.us or import the preview or purchased version from TeachersPayTeachers.com.