Practice Problems on Finite and Infinite Sets

Finite and infinite sets are two different parts of "Set theory" in mathematics. When a set has a finite number of elements, it is called a "Finite set" and when a set has an infinite number of elements, it is called an "Infinite set". A finite set is countable, whereas an infinite set is uncountable. The elements in a finite set are natural numbers i.e., non-negative integers. We use dots in a set to represent an infinite set.

Solving practice problems on Finite and Infinite Sets are the best way to get a solid understanding of the concept. In this articles we will discuss about the finite and infinite sets, their properties, solved problems and practice Problems on Finite and Infinite Sets.

Finite Sets

A finite set has a finite or countable number of elements. It is a set of natural numbers i.e., positive integers and can be easily counted. It is expressed as P = {1, 2, 3, 4, . . ., n} for natural number n. For example, {5, 6, 7, 8} is a set of countable numbers. An empty set { } is also considered a finite set as it has zero elements i.e., P={ } or n(A) = 0.

Example of Fine Sets

• A set of days in a week: ( Sunday, Monday, Tuesday, Wednesday, Thursday, Friday and Saturday )
• The set of natural numbers less than 10: {1, 2, 3, 4, 5, 6, 7, 8, 9}
• The set of vowels in the English alphabet: {a, e, i, o, u}
• The set of planets in the Solar System: {Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune}

Infinite Set

An infinite set, as the name suggests, has an infinite or uncountable number of elements. It is a set of all whole numbers including non-negative and negative integers. Infinite sets are also known as uncountable sets. We know that two infinite sets always form an infinite set. It is expressed as P = {0, 1, 2, 3, . . . }, a set of all the whole numbers.

Examples of Infinite Sets

• Set of whole numbers
• Set of integers
• Line segments in a plane etc.

Practice Problems on Finite and Infinite Sets - Solved Examples

1: Let A= {1,2,3,4} and C= {4,5,6,8} are finite sets. Find the union and intersection of sets A and C.

• The union of two sets A and C can be written as A∪C. It is the set of all the unique elements of both the sets A and C.

Therefore, A∪C = {1,2,3,4,5,6,8}.

• The intersection of the two sets A and C is written as A∩C, is the set of elements which are common in both the sets.

Therefore, A∩C = {4}.

2: Let P = {1,2,3,4,5,6} be a finite set. How many subsets does set P have?

• To calculate the subsets of a set, we will use the formula 2ⁿ , where n= the number of elements in the set.

Now, in this question, n= 5

The number of subsets = 2ⁿ =2⁵ = 32.

Therefore, the set P has 32 subsets including the empty set and the set itself.

3: State whether the given set is finite or infinite?

1) {1,3,5, . . . }

2) {2, 3, 4, 5}

3) { . . . , -3, -2, -1, 0, 1, 2, 3}

4) {10, 20, 30, . . . 200}

1) Infinite

2) Finite

3) Infinite

4) Finite

4: State whether the given set is finite or infinite?

1) {0}

2) {Φ}

3) {X │X∈ N and X>10}

4) { X │X is a prime number}

1) Finite

2) Finite

3) Infinite

4) Infinite

5: If Tan θ = 1, then the solution set of the equation is finite or infinite?

Given that tan θ = 1

⇒ tan θ = 1 = tan ?/4

⇒ θ = n? + ?/4 , where n∈Z

⇒ θ = { X : X∈ (n? + ?/4), n∈Z }

The solution of the given question is an infinite set.

6: Consider the following statement:

1) P = {X : X is prime, such that 1> X >10} and A = {2,3,5,7} are equal sets.

2) P = {a,e,i,o,u} and Q = {a,i,o,e,u} are unequal sets.

Which of the following statement is correct?

1) Given, X is prime such that 1> X >10

hence X = 2,3,5,7

P = {2,3,5,7} = A⇒ P=A

Therefore both the sets are equal and the statement is correct.

2) Given, P = {a,e,i,o,u} and Q = {a,i,o,e,u} are unequal sets.

where the order of the elements in a set does not impact the equality of the two sets.

Hence, set P and set Q are equal and the given statement is incorrect.

7: Find out whether the following set is finite or not.

A = {X : X∈N and (X-1) (X-2) = 0}

Given (X-1) (X-2)=0

X= 1,2 then the given set is= (1,2)

As the set has two elements and is countable,

Hence, the set is finite.

8: Identify the set is finite or infinite?

(1, 1/2, 1/4, 1/8, . . . )

The given set is infinite as it has no end point within the set.

9: Find out whether the following site is finite or infinite?

A = {X: X ∈ N and X² = 4}

Given, X² = 4

⇒ X= +2 or -2

⇒ X = 2,-2 but X is a natural number, it can not be negative, hence X = 2

therefore A = (2) which is countable. The set is a finite set.

Read More,

• Set theory
• Finite sets
• Infinite sets

Practice Problems on Finite and Infinite Sets

These Practice Problems on Finite and Infinite Sets will help you to test your understanding of the concept

1: A= {X:X∈R such that X²-7X+12 = 0}, then A is a finite or an infinite set?

2: Let A = {1,2,3,4,5} and B= {4,5,6,7,8}, then A∩B is finite or infinite?

3: Let A = {2, 4, 6, 8, 10} and B = {1, 3, 5, 7, 9} be two finite sets. Find the cardinality of the A∪B.

4: let you have two finite sets that have m and n elements, in how many ways you can create a new set by combining elements from both the sets?

5: Let A ={2,4,6,8,10}, how many subsets does the set A have?

6: Check whether the given sets are finite or infinite:

• Factors of 25 ,
• Multiples of 2,
• Lines segments in a plane

7: Proof the power set of set B = {3, 5, 7 . . . } is an infinite set.

8: Check whether the given sets are finite or infinite:

• P = {2, 4, 6, . . . }
• M = {1, 2, 3, 4, 5}
• X = {a, b, c, . . . }