Class 11 Maths Chapter 1 Sets NCERT Solutions | Complete Guide with Examples & Questions

 Class 11 Maths Chapter 1 Sets NCERT Solutions | Complete Guide with Examples & Questions

Class 11 Maths Chapter – Sets

Class 11 Maths Navigation ...................................................................................................................

Introduction

Sets are one of the most basic and important topics in mathematics. Almost every chapter in higher maths uses set concepts in some form.

A set is simply a collection of well-defined objects.

Examples:
A = {1, 2, 3, 4}
B = {a, e, i, o, u}

Basic Definitions

Set: A collection of objects
Element: Objects inside a set
Empty Set: A set with no elements → ∅
Finite Set: Limited number of elements
Infinite Set: Unlimited elements

Types of Sets

  • Equal Sets: Same elements

  • Equivalent Sets: Same number of elements

  • Subset: A ⊆ B

  • Proper Subset: A ⊂ B

Important Formulas

Number of Subsets

Number of subsets=2n\text{Number of subsets} = 2^n

Union and Intersection

$$n(A \cup B) = n(A) + n(B) - n(A \cap B)$$


Complement

A=UAA' = U - A

Venn Diagram Concept

Venn diagrams help in visual understanding of sets.
Circles represent sets and overlapping regions show common elements.

Solved NCERT Examples (Step by Step)

Example 1

Write the set of all vowels in English alphabet.

Solution:
A = {a, e, i, o, u}

Example 2

Find whether A = {1,2,3} and B = {3,2,1} are equal.

Solution:
Both sets have same elements
So, A = B

Example 3

If A = {1,2,3} and B = {2,3,4}, find A ∪ B.

Solution:
A ∪ B = {1,2,3,4}

Example 4

Find A ∩ B.

Solution:
Common elements = {2,3}

Example 5

Find number of subsets of A = {1,2,3}

Solution:
n = 3

Number of subsets = 2³ = 8

Example 6

If U = {1,2,3,4,5} and A = {2,3}, find A'

Solution:
A' = {1,4,5}

Example 7

Find A − B where A = {1,2,3} and B = {2}

Solution:
A − B = {1,3}

Example 8

Find B − A

Solution:
B − A = {} = ∅

Example 9

If n(A)=20, n(B)=15, n(A∩B)=5, find n(A∪B)

Solution:
n(A∪B) = 20 + 15 − 5 = 30

Example 10

Check whether {1,2} ⊂ {1,2,3}

Solution:
Yes, it is a proper subset

Exercise Based Practice Questions

You should practice:

  • Writing sets in roster form

  • Set builder form

  • Union and intersection problems

  • Venn diagram questions

  • Complement and subset problems

15 FAQs 

1. What is a set?
A set is a collection of well defined objects.
2. What is empty set?
A set with no elements is called empty set (∅).
3. What is subset?
If all elements of A are in B then A ⊆ B.
4. What is proper subset?
A ⊂ B when A is subset but not equal to B.
5. What is universal set?
Set containing all elements under discussion.
6. What is union?
A ∪ B contains all elements of A and B.
7. What is intersection?
A ∩ B contains common elements.
8. What is complement?
Elements not in A but in universal set.
9. What is power set?
Set of all subsets of a set.
10. Formula of subsets?
2ⁿ where n is number of elements.
11. What is difference of sets?
A − B contains elements of A not in B.
12. What is cardinal number?
Number of elements in a set.
13. What is Venn diagram?
Diagram to represent sets using circles.
14. What is equal set?
Sets having same elements.
15. What is equivalent set?
Sets having same number of elements.

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