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5.3 Study Guide Prime/Composite & Odd/Even Learning Goals 5.3 a) identify and describe the characteristics of prime and composite numbers; and b) identify and describe the characteristics of even and odd numbers. Vocabulary Divisible - capable of being divided by another number without a remainder Even - any number ending in 0, 2, 4, 6, or 8 Odd - any number ending in 1, 3, 5, 7, or 9 Natural Number - the counting numbers Prime Number - a natural number with exactly two factors (itself and one) Composite Number - any natural number with more than two factors Product – the answer in multiplication Factor - a number that is multiplied by another number to find a product. Example: factor x factor = product Multiple - the product of that number and any other whole number Example: the multiples of 3 are 3,6, 9, 12… Practice at Home Practice identifying prime and composite numbers (to 100) by using the following steps to determine if a number is prime or composite: Prime # 2 3 Composite Numbers Multiples of 2 Multiples of 3 Divisibility Rule Even numbers > 2 If the sum of the digits of a number is divisible by 3, then the number is divisible by 3. Example: 78 - 7+8=15 (a multiple of 3) so 78 is divisible by 3. 5 7 Multiples of 5 Multiples of 7 Numbers ending in 0 and 5 This rule is quite complicated. Students can use calculator to determine if it is divisible by 7. ** The number 1 is neither prime nor composite. To determine if a number is odd or even, look at the ONES place. 786 is EVEN because there is a 6 in the ones place. 483 is ODD because there is a 3 in the ones place Sample Questions 1. Which is a prime number? A B C D 2. Which is a composite number? A B C D 3. 1 2 3 4 Which number is even? A B C D 7. 45 67 86 91 Which number is neither prime nor composite? A B C D 6. 31 49 79 97 Which number is not composite? A B C D 5. 7 9 17 19 Which number is not prime? A B C D 4. 2 4 18 27 27 34 41 63 Which number is odd? A B C D 36 43 50 78