Sets

1. INTRODUCTION
TO SETS

2. OBJECTIVES:
•Define set,
•Describe and illustrate well-defined sets and
null sets,
•Determine the elements of a given set, and
•Identify the number of elements or its
cardinality

3. UNLOCKING WORDS
DIFFICULTY
•Integers {-∞, 0, +∞}
•Whole numbers { 0, 1, 2, 3, 4, 5, …}
•Counting/natural numbers { 1, 2, 3, 4, 5, …}
•Even numbers {2, 4, 6, 8, …}
•Odd numbers { 1, 3, 5, 7, 9, …}

4. UNLOCKING WORDS
DIFFICULTY
•Prime numbers {2, 3, 5, 7, 11, …}
•Composite numbers {4, 6, 8, 9, 10, …}
•Perfect squares { 1, 4, 9, 16, 25, …}
•Multiples {skip counting by…}
•Factors { numbers which can be divided without
a remainder}

5. ACTIVITY:
A B C

6. A = {
} A = { shoe, jacket, cap }
B = {
} B = { orange, mango, banana }
C = {
} C = { ball, toy car, doll}

7. A = { shoe, jacket, cap }
B = { orange, mango, banana
}
C = { ball, toy car, doll}
A = { set of objects that can be worn}
B = { set of fruits}
C = { set of toys}
S
E
T

8. SET
- A set is a group or collection of objects.
It is named using CAPITAL letter. Each
object in a set is called a member or an
element of a set.

9. ELEMENT
∈ - the symbol used for element
∉ - the symbol used for not an element

10. EXAMPLE:
1. A = {school days in a week}
A = { Mon, Tue, Wed, Thurs, Fri}
Mon, Tue, Wed, Thurs, Fri. are called members
or elements of a given sets
Monday ∈ A Thursday ∈ A Sunday ∉ A

11. 2. B = {counting numbers less than 5}
B = {1, 2, 3, 4}
1, 2, 3, 4, are called members or elements of a given set.
3. C = {primary colors}
C = {Red, Blue, Yellow}
Red, Blue, Yellow are called members or elements of a
given set.
EXAMPLE:

12. ACTIVITY:
A = {even numbers}
B = {odd numbers}
C = {counting numbers}
Fill in the blank with the symbol of an element(∈ ) or not an
element(∉) of a given set
2____A 7____C -2____C
8____B 3____B 5____A
0____C -1___B -4____A
∉
∈ ∈ ∉
∈
∈
∉ ∈
∉

13. WELL-DEFINED SET
A = {Primary colors} - well defined set
B = {set of beautiful girls in school} - not well defined set
C = {set of months in a year} - well defined set
D = {set of popular actors} – not well defined set
E = { set of excellent singers} – not well defined set

14. EMPTY OR NULL SET
A set with no members or elements. It is denoted by { }
for empty set and ∅ for null set.
Examples:
A = {set of triangles with 4 sides}
B = {set of motnths in a year start with B}
C = {set of whole numbers less than 0}

15. CARDINALITY
Refers to the number of elements in a given set. It is
denoted by the symbol n.
“Cardinality of set A” is written as n(A).

16. EXAMPLE:
A = {set of primary colors}
A = {Red, Blue, Yellow}
B = { school days in a week}
B = {mon, tue, wed, thurs, fri,}
– n(A) = 3
– n(B) = 5