Am I Prime ?

Designed by: Tammy Hester      School: Gibbes Middle

Grade: 7      Subject: Mathematics

Core Curriculum Objective:  Explore and identify the concepts of primes and composites.   (7NR4-10)

South Carolina Curriculum Standards: Number and Numeration Systems (D. 1.)

Overview: Students will use technology to explore prime numbers. Students will be able to determine whether a number is prime or composite.

Focus Question: What do 3, 17, 2, and 19 have in common?

Time Frame: Two 50-minute class periods

Resources: computer Website: www.forum.swarthmore.edu/dr.math/faq/faq.prime.num.html 

www.forum.swarthmore.edu/mathgrepform.html 

 www.forum.swarthmore.edu/dr.math/faq/faq.divisibility.html 

 www.utm.edu/research/primes/largest.html

 www.rsok.com/~jrm/printprimes.html

Assessment: Students will determine whether a number is prime or composite. Students will explain the definition of prime. Students will explore different websites discovering prime numbers.

Day One:

Activity One

The teacher will introduce the topic of prime numbers after the focus question. The teacher should ask students how they would go about listing all the prime numbers between 1 and 100. Allow time for students to give their suggestions. Tell the students that the website they will visit shows one way to find all the prime numbers between 1 and 100.

Students will visit Website www.forum.swarthmore.edu/dr.math/faq/faq.prime.num.html

Students should find and record the definition of prime in their vocabulary section of their notebooks. Students should then scan down to the "Sieve of Eratosthenes." (A copy is provided in this lesson plan.) Following the instructions with Dr. Math students should complete the sieve activity. After the students have finished the sieve they can scan back up the page to check if they have all of the prime numbers between 1 and 100 identified. The teacher should explain the assessment and monitor as the students are completing the activity.

Activity Two

The teacher will explain to the students that the next search is simply one for more information about prime numbers. Students will find many interesting things in the section on prime numbers. Students will pick their 3 favorite findings to share at a later date with classmates.

Students should then click on "The Largest Known Primes". After reaching this, click on Introduction (What are primes? Who cares?) Students should read this section carefully and record (in their math journals) at least 3 things they learn from this section.

Activity Three

This activity focuses on the divisibility rules. The teacher should give an example of how divisibility rules can help determine if a number is prime.

Go back to the Dr. Math page 

Click on "Search the Dr. Math Archives" 

Type in prime number and hit search.

Click on Math Forum: Divisibility Rules

Students should put the divisibility rules for 2,3,4,5,6,9, and 10 in their notebooks.

The teacher should discuss each divisibility rule with the students and give examples of each rule. After all of the rules have been discussed the teacher should give the students a number and then ask the students to use the rules to decide if it is divisible by 2? 3?, etc

For example: The teacher may give the number 510 and ask is this number divisible by 5? When a student answers they must state the rule for proof.

These rules should be memorized. Students may wish to add some of the other rules as well, but the ones listed are a requirement.

Day Two

Activity Four

The teacher should introduce the concept of prime factorization, explaining that all composite numbers can be broken down into a prime factorization. The teacher should do at least two example with the students before allowing students to go the website. The teacher should ask students if a prime factorization could have a zero or one listed. The teacher should tell the students to search the following website to find answers to the questions listed below.

Return to website 

www.forum.swarthmore.edu/dr.math/faq/faq.prime.num.html Students should scan down until they see in bold print Dr. Math Archives: Scan down and click on the following to answer the questions. Students should answer the following questions and put the answers in the journal section of their math notebooks.

1. Click on Is Zero Prime or Composite.  Record your findings. 

2. Click on Why is One Not Considered Prime.  Record your findings. 

3. Click on Prime Factorization.  Record a definition, explanation and example.

A class discussion should be held after students have had time to record their findings. The teacher should give two or three numbers and ask the students to do the prime factorization of each. The teacher may ask for volunteers to put their work on the board and monitor to make sure all students have an understanding of prime factorization.

Activity Five

The teacher should once again go over the definition of prime. The teacher should explain that there are an infinite number of prime numbers. Do not let students think prime numbers are only between 1 and 100.

Explain that the next site will allow them to find prime numbers greater than 100. Explain that the next website is a "fun site" to experiment with finding different prime numbers.

Students should go to website: www.rsok.com/~jrm/printprimes.html

Students should pick two numbers. The numbers they choose must have a range of at least 50 but no more than 100. Students can then list all of the prime numbers found between their two numbers. The numbers chosen and the primes between should be recorded in the journal section of their notebooks.

****This is simply a fun activity and students may want to experiment with several pairs of numbers. Students should be monitored and stick to the range given of the two numbers they choose. *** The range should not be too large to avoid running the web browser out of memory****

Activity Six

Students should complete the Assessment of prime numbers and prime factorization provided in the lesson plan.

Name _____________________________Date __________Period_______

Prime Number Assessment

Determine if the following numbers are prime or composite. Label with P or C. You may use your divisibility rules.

Prime Factorization Assessment

Use a factor tree to help break the numbers down into their prime factorization.

Name ____________________ Date __________Period______

Rubric for Prime Activities