NCERT Class 11 Mathematics Mathematics: Chapter 8 — 1 Introduction

Reviewed by NCERT Help Editorial Team · Reviewed on 29 Jul 2026 · Last updated 10 Aug 2026 · Reading time 4 minutes

NCERT CBSE Class 11 Mathematics Mathematics Chapter 8 English PDF

This chapter introduces the concept of sequences and series in Mathematics for Class 11 CBSE students. It defines a sequence as an ordered collection of objects, with terms denoted by a1, a2,..., an. Finite and infinite sequences are explained with examples like ancestors and successive quotients. The chapter highlights how sequences can be represented by algebraic formulas, such as an = 2n for even natural numbers and an = 2n - 1 for odd natural numbers. It also introduces the Fibonacci sequence, defined by a recurrence relation. The chapter lays the groundwork for understanding progressions and their applications, preparing students for further study in arithmetic and geometric means, and special series.

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Quick info

Board	CBSE / NCERT
Class	Class 11
Subject	Mathematics
Book	Mathematics
Chapter	Chapter 8 — 1 Introduction
Language	English
PDF type	NCERT Textbook
Session	CBSE 2026
Reading time	4 minutes
Word count	699

Learning outcomes

Understand the definition and notation of sequences.
Differentiate between finite and infinite sequences.
Identify and represent sequences using algebraic formulas.
Recognize and understand the Fibonacci sequence.
Grasp the foundational concepts for progressions and series.

Vocabulary

Word	Meaning
Sequence	An ordered collection of objects, usually numbers.
Term	Each individual number in a sequence.
nth term / General term	The term at the nth position in a sequence, often represented by an.
Finite sequence	A sequence with a limited, fixed number of terms.
Infinite sequence	A sequence that continues without end.
Progression	A sequence that follows a specific pattern, often arithmetic or geometric.
Recurrence relation	A formula that defines each term of a sequence based on preceding terms.
Fibonacci sequence	A sequence where each term is the sum of the two preceding ones, starting from 0 and 1 (or 1 and 1).

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Practice questions

What is the 5th term of the sequence defined by an = 3n + 2? Answer: 17 (a5 = 3*5 + 2 = 15 + 2 = 17)
Is the sequence 2, 4, 6, 8,... a finite or infinite sequence? Explain. Answer: Infinite, because it continues indefinitely with the pattern of even numbers.
Write the first three terms of the Fibonacci sequence if a1 = 1 and a2 = 1. Answer: 1, 1, 2 (a3 = a1 + a2 = 1 + 1 = 2)

Practice MCQs

Q1. What is the general term for the sequence of odd natural numbers?

Q2. A sequence with a fixed number of terms is called:

Q3. In the Fibonacci sequence, a_ $n = a_{n-2} + a_{n-1}. If a_1$ = 1 and $a_2$ = 1, what is $a_4$ ?

Q4. The sequence of even natural numbers can be represented by:

Q5. Which of the following is an example of a sequence?

Frequently asked questions

What is a sequence in mathematics?

A sequence is an ordered list of numbers or objects, where each element is called a term and has a specific position.

What is the difference between a finite and an infinite sequence?

A finite sequence has a limited number of terms, while an infinite sequence continues without end.

How can the terms of a sequence be represented?

Terms can be represented by listing them (e.g., 2, 4, 6,...) or by an algebraic formula called the general term or nth term (e.g., an = 2n).

What is the Fibonacci sequence?

The Fibonacci sequence is a special sequence where each number is the sum of the two preceding ones, usually starting with 0 and 1 or 1 and 1.

What is a recurrence relation?

A recurrence relation is a formula that defines a sequence by relating each term to previous terms.

What is the nth term of a sequence?

The nth term, denoted by an, is the general formula that gives the value of the term at any position 'n' in the sequence.

Related resources

Important topics

Definition and Notation of Sequences Finite vs. Infinite Sequences Algebraic Formula for nth Term Fibonacci Sequence Introduction to Progressions

Topics covered

Introduction to Sequences Definition of a Sequence Terms of a Sequence General Term (nth term) Finite Sequences Infinite Sequences Algebraic Representation of Sequences Fibonacci Sequence Recurrence Relations Sequences and Progressions Applications of Sequences

NCERT Class 11 Mathematics — Mathematics — Chapter 8 — 1 Introduction. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.