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Types of Sets

Depending on the number of elements contained by the sets, they are classified into the following types:

• Empty or Null set
• Unit or Singleton set
• Finite and Infinite set
1. Empty or Null Set:
A set which does not contain any elements is called empty or null set. It is denoted by a symbolΦ called 'Phi'. For example:
A = {prime number between 8 and 10}
Since there is no prime number between 8 and 10. So, set A =Φ

2. Unit or Singleton Set:
A set containing only one element is called a unit set or singleton set. For example:
N = {whole number less than 1}
Since the whole number, less than 1 is 0 which is a single term. i.e N = {0}. So, the set N is said to be a unit or singleton set.

3. Finite and Infinite Set:
A set which contains a finite number of elements is called a finite set. For example:
A = {odd number between 5 and 15}
Here, A = {7, 9, 11, 13}
Since we can express the given set in cardinal number i.e. n(A) = 4, It is said to be a finite set.
A set containing never-ending elements (i.e. infinite number of elements) is called an infinite set. For example:
P = {x : x is a set of prime numbers} i.e. P = {1, 2, 3, 5, 7, 11, 13,.....................}.
The given set P is so large that we cannot express it in cardinal form. It has an infinite number of elements. So, it is an infinite set.
(Note: Infinite sets cannot be expressed in roster form)

Set Relations

Depending on the types of elements containing by two or more than two sets, the relationship between them can be presented in the following ways:

• Equal sets
• Equivalent sets
• Overlapping sets
• Disjoint sets
1. Equal Sets:
Two sets are equal to be equal if both the sets have exactly the same elements. The equals set is denoted by the symbol '='. For examples:
A = {a, b, c, d, e}
B = {e, d, c, b, a}
Here, n(A) = 4 and n(B) = 4. Hence sets A and B are said to be equal set and expressed as A = B.

2. Equivalent Sets:
Two sets are said to be equivalent sets if they contain the same number of elements. It is denoted by the symbol '↔' or '∼'. For examples:
A = {1, 2, 3, 4 ,5}
B = {p, q, r, s, t}
Here, n(A) = 5 and n(B) = 5. Since they have the same cardinal number so they are said to be equivalent set and is expressed as A∼ B.

3. Overlapping Sets:
Two or more than two sets are said to be overlapping sets if they consist at least one common element. For examples:
A = {2, 4, 6, 8, 10, 12}
B = {3, 6, 9, 12, 15}
In both sets A and B, 6 and 12 are common, so sets A and B are overlapping sets.

4. Disjoint Sets:
Two or more than two sets are said to be disjoint if they do not have any of the elements common. For example:
A = {1, 2, 3, 5, 7, 11}
B = {4, 12, 16, 20}
In both sets, A and B none of the elements are common so set, A and B are disjoint.

• Empty set is denoted by a symbolΦ called 'Phi'.
• The equals set is denoted by the symbol '='.
• It is denoted by the symbol '↔' or '∼'.
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Click on the questions below to reveal the answers

Solution :

Here , P = { a,e,i,o,u} and Q={a,b,c,d,e}

a) Now , P ∪ Q = { a,b,c,d,e,i,o,u }

The shaded region represents the elements of P ∪ Q.

b) P ∩ Q = { a,e}

The shaded region represents the elements of P ∩ Q.

c) P - Q = { i,o,u}

The sheded region represents the elements of P - Q .

d) Q - P={b,c,d}

The shaded region represents the elements of Q -P .

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4 types
5 types
2 types
3 types
• A set which does not contain any elements is called _______.

finite set
empty or null set
unit or singleton set
infinite set

φ
ø
Θ
Φ

unit set
infinite set
finite set
null set
• A set which contains a finite number of elements is called ______.

finite set
infinite set
singleton set
empty set

unit set
null set
infinite set
finite set

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