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PowerPoint created by Parsheena Berch Resource: JBHM material Pictures: Google Images Prime and Composite Numbers Bell Ringer: • Page 35 in JBHM binder (DOK 3) Focus/Introduction: • 1d: Model and distinguish between prime and composite numbers. (DOK 1) • Prime and composite numbers help us to work with numbers better. This will help us next week when we work with factors and multiples. Also, this will help when we work with fractions. • We can “tell” if a certain number can be divided by another number. For example, we know that 655 is divisible by 5 because the number ends with a five. Quickly, go over the divisibility rules again for 2, 3, 4, 5, 6, 9, and 10. Divisibility Rules: A number is divisible by ___ if… • 2 – The number is an even number, ending in 2, 4, 6, 8, 0. Example: • 124: It ends in 4, so it is divisible by 2. • 124 ÷ 2 = 62 Divisibility Rules: A number is divisible by ___ if… • 3 – The sum of the digits is divisible by 3. Example: • 150: The sum of the digits, 1 + 5 + 0 = 6, is divisible by 3, so 150 is divisible by 3. • 150 ÷ 3 = 50 Divisibility Rules: A number is divisible by ___ if… • 4 – The number is even and the last 2 digits form a number that is divisible by 4. Example: • 724: It is even, and the last two digits, 24, is divisible by 4, so 724 is divisible by 4. • 724 ÷ 4 = 181 Divisibility Rules: A number is divisible by ___ if… • 5 – The number ends in 0 or 5. Example: • 105: It ends in 5, so 105 is divisible by 5. • 105 ÷ 5 = 21 Divisibility Rules: A number is divisible by ___ if… • 6– The number is even, and the sum of its digits is divisible by 3. Example: • 450: It is even and the sum of the digits, 4 + 5 + 0 = 9, is divisible by 3, so 450 is divisible by 6. In other words, if the rule for 2 and the rule for 3 work, the number is divisible by 6. • 450 ÷ 6 = 75 Divisibility Rules: A number is divisible by ___ if… • 7 and 8 – These rules are too complicated to actually be shortcuts. Divisibility Rules: A number is divisible by ___ if… • 9 – The sum of the digits is divisible by 9. Example: • 450: The sum of the digits, 4 + 5 + 0 = 9, is divisible by 9, so 450 is divisible by 9. • 450 ÷ 9 = 50 Divisibility Rules: A number is divisible by ___ if… • 10 –The number ends in 0. Example: • 1250: It ends in 0, so 1250 is divisible by 10. • 1250 ÷ 10 = 125 Guided Practice: (DOK 1) • Composite Number- a natural number that has more than two factors. • Examples: the factors of 8 are 1, 2, 4, and 8. Since there are more than two factors, 8 is composite. • More Examples… • Prime Numbers- a number that has only two factors, 1 and itself. The GCF of two prime numbers is 1. • Examples: The only factors of 2 are 1 and 2. Since there are only two factors, it is prime. • More Examples… Independent Practice: (DOK 2) • Handout #1 Page 108 • I am going to guide you through the steps to this activity. You must pay attention to everything I say. If you don’t, you will mess your page up. • Cross out #1 because it is neither prime nor composite. • Circle #2, the first prime number, and shade all multiples of 2. • Circle #3, the next prime number, and shade all multiples of 3. • What is your method to finding the multiples? • Circle #5 and shade all multiples of 5. • Circle #7 and shade all multiples of 7. • Predict what will be the first multiple of 7. • Circle the next prime number, 11, and then predict what the next unmarked number is. • What is left? • Prime numbers Closure: • Define and give examples of each: • Prime numbers: _____________________ • Composite numbers: ____________________ • Superprime numbers: ___________________