SAT Prep Class
Unit 1: Algebra Review
Day 3: Factors and Multiples
Objectives:
Find the greatest common factor and least common multiple
Warm Up
1) For all positive integers a and b, let a∙b be defined by a∙b =
𝑎𝑏 +1
𝑎−1
What is the value of 4∙2?
A
B
C
D
E
2) Using the number line above: Which of the following must be true?
A) AC < CD
B) AC < CE
C) AD < CE
E) AD < DE
F) BD < DE
SAT Prep Class
Unit 1: Algebra Review
Day 3: Factors and Multiples
Objectives:
Find the greatest common factor and least common multiple
Vocabulary:
A factor of a whole number
Ex. Factors of 6
A prime number if a positive integer that has exactly
factors,
A composite is a positive integer that has more than
factors
and
Ex. Is 20 prime or composite?
The
numbers have in common
of two numbers is the largest facor the two
Ex. GCF of 16 and 36
The
is the smallest multiple two numbers have in common.
Ex. LCM of 5 and 8
Ex. LCM of 6 and 24
Divisibilty Rules:
Divisible by two: even numbers
Divisible by three: if the sum of the digits are divisible by 3, the number is divisible by 3
Divisible by four: if its last two digits are divisible by 4
Divisible by five: The number ends in a five or zero
Divisible by six: if divisible by 2 and 3
Divisible by nine: if the sum of the digits are divisible by 9
Even and Odd Rules:
Even x Even = Even
Even + Even = Even
Odd x Odd = Odd
Odd + Odd = Even
Even x Odd = Even
Even + Odd = Odd
Example 1: What is the greatest integer less than 1000 that has both 5 and 8 as factors?
Example 2: If y is an integer between 500 and 600, that is divisible by 3, 6, and 9, what is one
possible value of y.
Classwork: p. 21 and 22
Homework: p. 27 and 28