1.2 Factors and Multiples
Mme DiMarco
Learning Goal
 Learning Goal: the focus of today’s lesson is to
become familiarized with generating factors and
multiples of given numbers.
 We will be exploring ways in which numbers can
describe other numbers 
Explore!
 Analyse the numbers in the circles below.
Abundant
18
 Use a table to record the factors of each
number.
 Find the sum of the remaining factors
(not including the number itself as a
factor)
Number
Factors
20
12
Perfect
6
Deficient
15
Sum of Factors
7
8
Results?
Number
Factors
Sum of Factors (not
including number itself)
18
1 ,2, 3, 6, 9, 18
21
12
1, 2, 3, 4, 6, 12
16
20
1, 2, 4, 5, 10, 20
22
15
1, 3, 5, 15
9
7
1,7
1
8
1,2,4,8
7
6
1,2,3,6
6
 Why do you think a number is called “ abundant ”,
“deficient” or “perfect”?
Abundant, Deficient and Perfect
Numbers
 Abundant Number: the sum of all factors (not including the number itself) is GREATER than the
number itself




Example: 20
Factors (1, 2, 4, 5, 10, 20)
Sum of factors (excluding 20) 1 + 2+ 4 + 5 + 10 = 22
22 > 20, therefore 20 is abundant
 Deficient Number: the sum of all factors (not including the number itself) is LESS than the
number itself




Example: 15
Factors (1, 3, 5, 15)
Sum of factors (excluding 15) 1 + 3 + 5 = 9
9 < 15, therefore15 is deficient
 Perfect Number: the sum of all factors (not including the number itself) is EQUAL to the number
itself




Example: 6
Factors: 1, 2, 3, 6
Sum of factors (excluding 6) 1 + 2 + 3 = 6
6 = 6, therefore 6 is a perfect number
Factors
Recall…
 Factor: a number that divides exactly into another number
 Example: the factors of 6 are 1, 2, 3 and 6
 Prime Number: a number with only 2 factors, itself and 1.
 Examples: 2, 3 and 5
 Composite Number: a number with more than 2 factors.
 Examples: 8, 16 and 20
 Common Factors: factors that are the same for 2 numbers
Greatest Common Factor
 Greatest common factor: the greatest number that
divides into each number in a set.
 What is the greatest common factor of 12 and 30?
 Step 1: find all of the factors of 12 and 30
 12: 1, 2, 3, 4, 6, 12
 30: 1, 2, 3, 5, 6, 10, 15, 30
 Step 2: highlight/circle all factors in common
 Factors in common: 1, 2, 3, 6
 Step 3: find the highest common factor
 GCF: 6
Multiples
 Multiples: found by multiplying the number by 1, 2, 3
and so on or by skip counting
 Multiples of 10: 10, 20, 30 40, 50 …
 Common Multiples: multiples that are the same for
two numbers
 Lowest Common Multiple (LCM): the lowest multiple
that is that same for two numbers
Finding the Lowest Common Multiple
 Step 1: list the multiples of each number
 Multiples of 10: 10, 20, 30, 40, 50 ..
 Multiples of 5: 5, 10, 15, 20 ..
 Step 2: find the lowest common multiple among
those that are in common
 Multiples of 10: 10, 20, 30, 40, 50 ..
 Multiples of 5: 5, 10, 15, 20 ..
Homework 
 Pages 16 – 17
 Questions 1 – 6, 8, 9