Stimulating Understanding of Computational science through Collaboration, Exploration, Experiment, and Discovery for students with Hearing Impairments
a collaboration of the Shodor Education Foundation, Inc., Eastern North Carolina School for the Deaf, Barton College, the National Technical Institute for the Deaf, and Interpreters, Inc.

For Teachers!

The Sieve of Eratosthenes

Lesson Plan Suggestion: 

Focus and Review: Do a quick review of division. Explain the concept of sieve, using the analogy of straining
pasta through a colander. Tell the students that the point of using a colander is to get rid of the water, while
keeping the noodles. This is called a sieve. Introduce the students to the words and signs for prime and composite
numbers. 
Statement of Objectives: Tell the students that they are going to be learning about prime and composite numbers
today. To do this, they need to use something called the Sieve of Eratosthenes. 
Teacher Input: Briefly, in your own words, explain the concepts on the student page. Make sure to give a brief
explanation and examples of prime and composite numbers. Have the students watch the sign explanation for the
student page. Then, have them read the Math Behind the Model. Ask if they have any questions. 
Guided Practice: Give the students example numbers, such as 2, 3, 4, and 5. Have the students decide if they are
prime or composite. Practice doing this until the students have a basic understanding of the difference between
prime and composite numbers. 
Independent Practice: The students will work through the Sieve of Eratosthenes model. The program is
self-guided, but the students might still need some help if they have problems. For an explanation of how the
program is designed to work, see the Help Running the Model for using the program. 
Conclusion: Talk to the students about their results. What numbers were prime? How did they know they were
prime? What patterns did they notice when crossing off 2 and 5? Was there a pattern with 3 and 7? What other
patterns did the students notice during their work? If given a number, would they know if it is prime? Have them
explain the process of the sieve. Work together, as a class, and list the steps. 

After the students have finished this lesson,  show them the First 100 Prime Numbers and a Large Prime
Number . As a follow up activity have them read the explanation Why Do We
Need Primes? This will help them understand how prime numbers are important to our society.

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This project is supported, in part, by the National Science Foundation Opinions expressed are those of the authors and not necessarily those of the National Science Foundation.