1 Sets It is natural for us to classify items into .docx

1
Sets
It is natural for us to classify items into groups, or sets, and
consider how those sets overlap
with each other. We can use these sets understand relationships
between groups, and to
analyze survey data.
Basics
An art collector might own a collection of paintings, while a
music lover might keep a
collection of CDs. Any collection of items can form a set.
Set
A set is a collection of distinct objects, called elements of the
set.
A set can be defined by describing the contents, or by listing
the elements of the set,
enclosed in curly brackets.

Example 1
Some examples of sets defined by describing the contents:
a) The set of all even numbers
b) The set of all books written about travel to Chile
Some examples of sets defined by listing the elements of the
set:
a) {1, 3, 9, 12}
b) {red, orange, yellow, green, blue, indigo, purple}
A set simply specifies the contents; order is not important. The
set represented by {1, 2, 3} is
equivalent to the set {3, 1, 2}.
Notation
Commonly, we will use a variable to represent a set, to make it
easier to refer to that set
later.
The symbol ∊ means “is an element of”.

A set that contains no elements, { }, is called the empty set and
is notated ∅
Example 2
Let A = {1, 2, 3, 4}
To notate that 2 is element of the set, we’d write 2 ∊ A
2
Sometimes a collection might not contain all the elements of a
set. For example, Chris owns
three Madonna albums. While Chris’s collection is a set, we
can also say it is a subset of the
larger set of all Madonna albums.
Subset
A subset of a set A is another set that contains only elements
from the set A, but may
not contain all the elements of A.

If B is a subset of A, we write B ⊆ A
A proper subset is a subset that is not identical to the original
set – it contains fewer
elements.
If B is a proper subset of A, we write B ⊂ A
Example 3
Consider these three sets
A = the set of all even numbers B = {2, 4, 6} C = {2, 3, 4, 6}
Here B ⊂ A since every element of B is also an even number, so
is an element of A.
More formally, we could say B ⊂ A since if x ∊ B, then x ∊ A.
It is also true that B ⊂ C.
C is not a subset of A, since C contains an element, 3, that is
not contained in A

Example 4
Suppose a set contains the plays “Much Ado About Nothing”,
“MacBeth”, and “A
Midsummer’s Night Dream”. What is a larger set this might be
a subset of?
There are many possible answers here. One would be the set of
plays by Shakespeare. This
is also a subset of the set of all plays ever written. It is also a
subset of all British literature.
Try it Now 1
The set A = {1, 3, 5}. What is a larger set this might be a
subset of?
3
Union, Intersection, and Complement
Commonly sets interact. For example, you and a new roommate
decide to have a house
party, and you both invite your circle of friends. At this party,

two sets are being combined,
though it might turn out that there are some friends that were in
both sets.
Union, Intersection, and Complement
The union of two sets contains all the elements contained in
either set (or both sets).
The union is notated A ⋃ B.
More formally, x ∊ A ⋃ B if x ∊ A or x ∊ B (or both)
The intersection of two sets contains only the elements that are
in both sets.
The intersection is notated A ⋂ B.
More formally, x ∊ A ⋂ B if x ∊ A and x ∊ B
The complement of a set A contains everything that is not in the
set A.
The complement is notated A’, or Ac, or sometimes ~A.
Example 5
Consider the sets: A = {red, green, blue} B = {red, yellow,
orange}
C = {red, orange, yellow, green, blue, purple}

a) Find A ⋃ B
The union contains all the elements in either set: A ⋃ B = {red,
green, blue, yellow, orange}
Notice we only list red once.
b) Find A ⋂ B
The intersection contains all the elements in both sets: A ⋂ B =
{red}
c) Find Ac ⋂ C
Here we’re looking for all the elements that are not in set A and
are also in C.
Ac ⋂ C = {orange, yellow, purple}
Try it Now 2
Using the sets from the previous example, find A ⋃ C and Bc ⋂
A
Notice that in the example above, it would be hard to just ask
for Ac, since everything from

the color fuchsia to puppies and peanut butter are included in
the complement of the set. For
this reason, complements are usually only used with
intersections, or when we have a
universal set in place.
4
Universal Set
A universal set is a set that contains all the elements we are
interested in. This would
have to be defined by the context.
A complement is relative to the universal set, so Ac contains all
the elements in the
universal set that are not in A.
Example 6
a) If we were discussing searching for books, the universal set
might be all the books in
the library.

b) If we were grouping your Facebook friends, the universal set
would be all your
Facebook friends.
c) If you were working with sets of numbers, the universal set
might be all whole
numbers, all integers, or all real numbers
Example 7
Suppose the universal set is U = all whole numbers from 1 to 9.
If A = {1, 2, 4}, then
Ac = {3, 5, 6, 7, 8, 9}.
As we saw earlier with the expression Ac ⋂ C, set operations
can be grouped together.
Grouping symbols can be used like they are with arithmetic – to
force an order of operations.
Example 8
Suppose H = {cat, dog, rabbit, mouse}, F = {dog, cow, duck,
pig, rabbit}
W = {duck, rabbit, deer, frog, mouse}

a) Find (H ⋂ F) ⋃ W
We start with the intersection: H ⋂ F = {dog, rabbit}
Now we union that result with W: (H ⋂ F) ⋃ W = {dog, duck,
rabbit, deer, frog, mouse}
b) Find H ⋂ (F ⋃ W)
We start with the union: F ⋃ W = {dog, cow, rabbit, duck, pig,
deer, frog, mouse}
Now we intersect that result with H: H ⋂ (F ⋃ W) = {dog,
rabbit, mouse}
c) Find (H ⋂ F)c ⋂ W
We start with the intersection: H ⋂ F = {dog, rabbit}
Now we want to find the elements of W that are not in H ⋂ F
(H ⋂ F)c ⋂ W = {duck, deer, frog, mouse}
5
De Morgan’s Laws
Augustus De Morgan, 19th century British mathematician,
developed a set of properties
known today as De Morgan’s laws. Simply stated, De Morgan
showed that the complement

of the union of two sets is the intersection of their
complements; likewise, the complement of
the intersection of two sets is the union of their complements.
De Morgan’s Laws
i) The complement of the union of two sets is the intersection of
their complements.
(A ⋃ B)’ = A’ ⋂ B’.
ii) The complement of the intersection of two sets is the union
of their complements.
(A ⋂ B)’ = A’ ⋃ B’.
Venn Diagrams
To visualize the interaction of sets, John Venn in 1880 thought
to use overlapping circles,
building on a similar idea used by Leonhard Euler in the 18th
century. These illustrations
now called Venn Diagrams.

Venn Diagram
A Venn diagram represents each set by a circle, usually drawn
inside of a containing
box representing the universal set. Overlapping areas indicate
elements common to
both sets.
Basic Venn diagrams can illustrate the interaction of two or
three sets.
Example 9
Create Venn diagrams to illustrate A ⋃ B, A ⋂ B, and Ac ⋂ B
A ⋃ B contains all elements in either set.
A ⋂ B contains only those elements in both sets –
in the overlap of the circles.
A B

A ⋃ B
6
Ac will contain all elements not in the set A. Ac ⋂ B
will contain the elements in set B that are not in set
A.
Example 10
Use a Venn diagram to illustrate (H ⋂ F)c ⋂ W
We’ll start by identifying everything in the set H ⋂ F
Now, (H ⋂ F)c ⋂ W will contain everything not in the set
identified above that is also in set
W.
H F
W

A B
A ⋂ B
A B
Ac ⋂ B
7
Example 11
Create an expression to represent the outlined part of the Venn
diagram shown.
The elements in the outlined set are in sets H and F,
but are not in set W. So we could represent this set as
H ⋂ F ⋂ Wc

Try it Now 3
Create an expression to represent the outlined portion of the
Venn diagram shown
A B
C
H F
W
H F
W
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Cardinality
Often times we are interested in the number of items in a set or
subset. This is called the
cardinality of the set.
Cardinality

The number of elements in a set is the cardinality of that set.
The cardinality of the set A is often notated as |A| or n(A)
Example 12
Let A = {1, 2, 3, 4, 5, 6} and B = {2, 4, 6, 8}.
What is the cardinality of B? A ⋃ B, A ⋂ B?
The cardinality of B is 4, since there are 4 elements in the set.
The cardinality of A ⋃ B is 7, since A ⋃ B = {1, 2, 3, 4, 5, 6,
8}, which contains 7 elements.
The cardinality of A ⋂ B is 3, since A ⋂ B = {2, 4, 6}, which
contains 3 elements.
Example 13
What is the cardinality of P = the set of English names for the
months of the year?
The cardinality of this set is 12, since there are 12 months in the
year.
Sometimes we may be interested in the cardinality of the union

or intersection of sets, but not
know the actual elements of each set. This is common in
surveying.
Example 14
A survey asks 200 people “What beverage do you drink in the
morning”, and offers choices:
Suppose 20 report tea only, 80 report coffee only, 40 report
both. How many people drink
tea in the morning? How many people drink neither tea nor
coffee?
This question can most easily be answered by
creating a Venn diagram. We can see that we can
find the people who drink tea by adding those who
drink only tea to those who drink both: 60 people.
We can also see that those who drink neither are

those not contained in the any of the three other
groupings, so we can count those by subtracting
from the cardinality of the universal set, 200.
200 – 20 – 80 – 40 = 60 people who drink neither.
Coffee Tea
20 80 40
9
Example 15
A survey asks: Which online services have you used in the last
month:
used both
The results show 40% of those surveyed have used Twitter, 70%
have used Facebook, and
20% have used both. How many people have used neither
Twitter nor Facebook?

Let T be the set of all people who have used Twitter, and F be
the set of all people who have
used Facebook. Notice that while the cardinality of F is 70%
and the cardinality of T is 40%,
the cardinality of F ⋃ T is not simply 70% + 40%, since that
would count those who use both
services twice. To find the cardinality of F ⋃ T, we can add the
cardinality of F and the
cardinality of T, then subtract those in intersection that we’ve
counted twice. In symbols,
n(F ⋃ T) = n(F) + n(T) – n(F ⋂ T)
n(F ⋃ T) = 70% + 40% – 20% = 90%
Now, to find how many people have not used either service,
we’re looking for the cardinality
of (F ⋃ T)c . Since the universal set contains 100% of people
and the cardinality of F ⋃ T =
90%, the cardinality of (F ⋃ T)c must be the other 10%.
The previous example illustrated two important properties
Cardinality properties
n(A ⋃ B) = n(A) + n(B) – n(A ⋂ B)

n(Ac) = n(U) – n(A)
Notice that the first property can also be written in an
equivalent form by solving for the
cardinality of the intersection:
n(A ⋂ B) = n(A) + n(B) – n(A ⋃ B)
Example 16
Fifty students were surveyed, and asked if they were taking a
social science (SS), humanities
(HM) or a natural science (NS) course the next quarter.
21 were taking a SS course 26 were taking a HM course
19 were taking a NS course 9 were taking SS and HM
7 were taking SS and NS 10 were taking HM and NS
3 were taking all three 7 were taking none
10

How many students are only taking a SS course?
It might help to look at a Venn diagram.
From the given data, we know that there are
3 students in region e and
7 students in region h.
Since 7 students were taking a SS and NS course, we
know that n(d) + n(e) = 7. Since we know there are 3
students in region 3, there must be
7 – 3 = 4 students in region d.
Similarly, since there are 10 students taking HM and
NS, which includes regions e and f, there must be
10 – 3 = 7 students in region f.
Since 9 students were taking SS and HM, there must be 9 – 3 =
6 students in region b.
Now, we know that 21 students were taking a SS course. This
includes students from regions

a, b, d, and e. Since we know the number of students in all but
region a, we can determine
that 21 – 6 – 4 – 3 = 8 students are in region a.
8 students are taking only a SS course.
Try it Now 4
One hundred fifty people were surveyed and asked if they
believed in UFOs, ghosts, and
Bigfoot.
43 believed in UFOs 44 believed in ghosts
25 believed in Bigfoot 10 believed in UFOs and ghosts
8 believed in ghosts and Bigfoot 5 believed in UFOs and
Bigfoot
2 believed in all three
How many people surveyed believed in at least one of these
things?

Try it Now Answers
1. There are several answers: The set of all odd numbers less
than 10. The set of all odd
numbers. The set of all integers. The set of all real numbers.
2. A ⋃ C = {red, orange, yellow, green, blue purple}
Bc ⋂ A = {green, blue}
SS
HM
NS
a
b
c
d
e
f
g
h
11
3. A ⋃ B ⋂ Cc

4. Starting with the intersection of all three circles,
we work our way out. Since 10 people believe in
UFOs and Ghosts, and 2 believe in all three; that
leaves 8 that believe in only UFOs and Ghosts. We
work our way out, filling in all the regions. Once we
have, we can add up all those regions, getting 91
people in the union of all three sets. This leaves 150
– 91 = 59 who believe in none.
Equal and Equivalent Sets
Often the terms equal and equivalent are used to describe sets.
These two terms are often
confused as being the same, however, they have a totally
different meaning.
Equal Sets
Two sets are equal if they both include the same exact elements.

Equivalent Sets
Two sets are equivalent if they have equal cardinalities.
Example 17
Let A = {2, 4, 6, 8}, B = {6, 2, 8, 4}, and C = {6, 3, 5, 1}.
Sets A and B are equal since they both include the same
elements: 2, 4, 6, 8.
Sets A and B are also equivalent since they both have the same
cardinality, n(A) = n(B) = 4.
Sets A and C are not equal since they include different
elements.
Sets A, B, and C are equivalent to one another since they all
have the same cardinality, n(A) =
n(B) = n(C) = 4.
Cartesian Product of Sets
The Cartesian product of two sets A and B, denoted by A × B, is
the set of all

possible ordered pairs whose first component is a member of the
first set and
whose second component is a member of the second set.
UFOs Ghosts
Bigfoot
30
8
28
3
2
6
14
59
12
Example 18
Let A = {6, 11} and B = {0, 1, 2}.
Find the Cartesian product of sets A and B.
The Cartesian product of A and B is as follows:

A × B = { {6, 0}, (6, 1}, {6, 2}, {11, 0}, {11, 1}, {11, 2} }
13
Exercises
1. List out the elements of the set “The letters of the word
Mississipi”
2. List out the elements of the set “Months of the year”
3. Write a verbal description of the set {3, 6, 9}
4. Write a verbal description of the set {a, i, e, o, u}
5. Is {1, 3, 5} a subset of the set of odd integers?
6. Is {A, B, C} a subset of the set of letters of the alphabet?
For problems 7-12, consider the sets below, and indicate if each
statement is true or false.
A = {1, 2, 3, 4, 5} B = {1, 3, 5} C = {4, 6} U =
{numbers from 0 to 10}
7. 3 ∊ B 8. 5 ∊ C 9. B ⊂ A 10. C ⊂ A 11. C ⊂ B 12. C ⊂ D

Using the sets from above, and treating U as the Universal set,
find each of the following:
13. A ⋃ B 14. A ⋃ C 15. A ⋂ C 16. B ⋂ C 17. Ac 18. Bc
Let D = {b, a, c, k}, E = {t, a, s, k}, F = {b, a, t, h}. Using
these sets, find the following:
19. Dc ⋂ E 20. Fc ⋂ D 21. (D ⋂ E) ⋃ F 22. D ⋂ (E ⋃ F)
23. (F ⋂ E)c ⋂ D 24. (D ⋃ E)c ⋂ F
Create a Venn diagram to illustrate each of the following:
25. (F ⋂ E) ⋃ D 26. (D ⋃ E)c ⋂ F
27. (F c ⋂ E c) ⋂ D 28. (D ⋃ E) ⋃ F
Write an expression for the shaded region.
29. 30.
A B
C

A B
C
14
31. 32.
Let A = {1, 2, 3, 4, 5} B = {1, 3, 5} C = {4, 6}. Find the
cardinality of the given set.
33. n(A) 34. n(B) 35. n(A ⋃ C) 36. n(A ⋂ C)
The Venn diagram here shows the cardinality of each set. Use
this in 37-40 to find the
cardinality of given set.
37. n(A ⋂ C) 38. n(B ⋃ C) 39. n(A ⋂ B ⋂ Cc) 40. n(A ⋂ Bc
⋂ C)
41. If n(G) = 20, n(H) = 30, n(G ⋂ H) = 5, find n(G ⋃ H)
42. If n(G) = 5, n(H) = 8, n(G ⋂ H) = 4, find n(G ⋃ H)
43. A survey was given asking whether they watch movies at

home from Netflix, Redbox, or
a video store. Use the results to determine how many people
use Redbox.
52 only use Netflix 62 only use Redbox
24 only use a video store 16 use only a video store and Redbox
48 use only Netflix and Redbox 30 use only a video store and
Netflix
10 use all three 25 use none of these
A B
C
A B
C
A
B
C
7
3
5

4
1
2
8
6
15
44. A survey asked buyers whether color, size, or brand
influenced their choice of cell
phone. The results are below. How many people were
influenced by brand?
5 only said color 8 only said size
16 only said brand 20 said only color and size
42 said only color and brand 53 said only size and brand
102 said all three 20 said none of these
45. Use the given information to complete a Venn diagram,
then determine: a) how many
students have seen exactly one of these movies, and b) how
many had seen only Star Wars.

18 had seen The Matrix (M) 24 had seen Star Wars (SW)
20 had seen Lord of the Rings (LotR) 10 had seen M and SW
14 had seen LotR and SW 12 had seen M and LotR
6 had seen all three
46. A survey asked people what alternative transportation
modes they use. Using the data to
complete a Venn diagram, then determine: a) what percent of
people only ride the bus, and b)
how many people don’t use any alternate transportation.
30% use the bus 20% ride a bicycle
25% walk 5% use the bus and ride a bicycle
10% ride a bicycle and walk 12% use the bus and walk
2% use all three
Module 1: Sets
Assignment 1
After studying the material in this module, please solve and

submit the following problems
from the module reading assignment on Sets from Math in
Society, by D. Lippman (v. 2.4):
#6, 14, 16, 20, 22, 26, 30, 34, 36, 44
- You must submit full answers and show all work to all
required problems to receive full
credit.
- You can use a word processor to type your work or you can do
all work on paper and scan
to a digital file to submit.
- Your assignment must be submitted as a single file (common
file types are pdf, doc, docx,
or image files).
- For questions requiring graphs you may use our web-based
calculator/grapher, Desmos
Calculator; you must create an account in order to be able to
save, print, share, or
download image files of your graphs.
file:///C:/Users/Admin/Documents/Classes/Broward%20College/
MGF1106/MGF1106%20OER%20MASTER%20COURSE/Text/
Sets.pdf
https://www.desmos.com/calculator
https://www.desmos.com/calculatorLocal DiskModule 1

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