Divisibility Factors and Primes Unit 4.1 and 4.2 Pages

1. 48 = = = = 1 x 20, 2 x 24, 4 x 5 1 x 16, 2 x 8, 4 x 4 1 x 19 1 x 18, 5 x 17 Warm Up Problems Find how many digits you can multiply together to create this number.

Divisibility, Prime Factorization. Objective: Students will use divisibility rules to determine if the number is prime or composite. They will then be able to break it into factors of prime numbers.

Definitions: DIVISIBLE DIVISIBLE: a number is divisible when it has no remainder left.

42 girls have signed up to play soccer this year. They only have 6 teams. Is it possible to have an equal amount of girls on each team? We need to split all the girls evenly into six groups. We will use Division to tell if this is possible When there is no remainder we are able to say 42 is divisible by

There are tricks to help up decide if a number is divisible by the numbers: 2, 3, 4, 5, 6, 7, , Add up the digits. Divisible by 3 or 9 Ends in 2, 4, 6, 8, 0 Divisible by Divisible by 2, 3 ends in 5, 0 Prime We only use digital sum for 3’s and 9’s… not for twos and not for 5’s, not for 4’s and 7’s prime and that’s how I know divisibility rules. (sung to the ants go marching)

3, What numbers are 610 divisible by? nds in an even number. Ends in an even number. Digits add up to be divisible by 3 or 9. Divisible by The number 4. Ends in a number 5 or 0. Divisible by the Number 6. Prime Ends in a zero

3, What numbers are 387 divisible by? nds in an even number. Ends in an even number. Digits add up to be divisible by 3 or 9. Divisible by The number 4. Ends in a number 5 or 0. Divisible by the Number 6. Prime Ends in a zero. 93

3, #1) What numbers are 508 divisible by? nds in an even number. Ends in an even number. Digits add up to be divisible by 3 or 9. Divisible by The number 4. Ends in a number 5 or 0. Divisible by the Number 6. Prime Ends in a zero. 2 4

3, #2) What numbers are 432 divisible by? nds in an even number. Ends in an even number. Digits add up to be divisible by 3 or 9. Divisible by The number 4. Ends in a number 5 or 0. Divisible by the Number 6. Prime Ends in a zero

3, #4) What numbers are 189 divisible by? nds in an even number. Ends in an even number. Digits add up to be divisible by 3 or 9. Divisible by The number 4. Ends in a number 5 or 0. Divisible by the Number 6. Prime Ends in a zero. 3 9

3, #3) What numbers are 247 divisible by? nds in an even number. Ends in an even number. Digits add up to be divisible by 3 or 9. Divisible by The number 4. Ends in a number 5 or 0. Divisible by the Number 6. Prime Ends in a zero. none

List all the factors of 18 = First we list all the factors in pairs , 2, 3, 6, 9, 18

List all the factors of 13 = First we list all the factors in pairs ,

#1) List all the factors of 12 = First we list all the factors in pairs , 2, 3, 4, 6,

#2) List all the factors of 21 = First we list all the factors in pairs , 3, 7,

#3) List all the factors of = First we list all the factors in pairs , 2, 4, 13, 26,

Homework Due: Wed. Dec. 2nd 4.1 page 158  page 163  9-12

4.2

Definitions: PRIME PRIME: a number is prime when it is only divisible by itself and 1. COMPOSITE COMPOSITE: a number that is divisible by more than one number.

Sometimes a number that cannot be divisible by any other number than a “1” is called: PRIME What numbers are 13 divisible by? 1 x 13 When a number can be divisible by more numbers than the number “1” is called: Composite What numbers are 45 divisible by? 3,9 5

Is the number 19 Prime or Composite Prime

Is the number 49 Prime or Composite Composite

Is the number 75 Prime or Composite Composite

Is the number 17 Prime or Composite Prime

Is the number 27 Prime or Composite Composite

Is the number 63 Prime or Composite Composite

6 2 x 3 = 6 Factors Whole numbers that are multiplied together to find another number (Product) are called FACTORS. Product

We write the prime factorization for the following number Using the TREE METHOD x 2 x 3 x First we choose any two factors to begin with, and keep going till it PRIME’s out. 22

We write the prime factorization for the following number Using the LADDER METHOD x 2 x 3 x 3 First we start with the smallest prime number, and keep dividing out till we get a final prime number

We write the prime factorization for the following number x 3 x 3 x 3 54

#5) Write the prime factorization for the following number x 2 x 2 x 2 x 3 Or 2 x

#6) Write the prime factorization for the following number x 2 x 5 Or 2 x

#7) Write the prime factorization for the following number x 3 x 11 66

#8) Write the prime factorization for the following number x 17 34

Homework 4.2 page 163 Due: Friday December 4th  5-8 and  17-24