### Mathematics Class XI

Unit-I: Sets and Functions
Chapter 1: Sets
Unit-II: Algebra
Chapter 5: Binomial Theorem
Unit-III: Coordinate Geometry
Chapter 1: Straight Lines
Chapter 2: Conic Sections
Unit-IV: Calculus
Unit-V: Mathematical Reasoning
Unit-VI: Statistics and Probability
Chapter 1: Statistics
Chapter 2: Probability

# Introduction to Permutation and Combination

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In this chapter, we shall learn some basic counting techniques which will enable us to answer the questions without actually listing the same arrangements. In fact these techniques will be useful in determining the number of different ways of arranging and selecting objects without actually listing them.

The fundamental principle of counting :

The fundamental principle is a rule used to count the total number of possible outcomes in a situation, it states that if there are ways of doing another thing after that, there are ways tp perform both of these actions.

Principle of multiplication :

If an event can occur in ‘ ’ different ways, following which another event can occur in’ ’ different ways, then the total number of different ways of simultaneous occurrence of both the events in a definite order is .

Principle of Addition :

If an event occurs in ‘ ’ different ways and another event wan occur in ‘ ’ different ways, then exactly one of the events can happen in ways.

Factorial ( ) :

The notation ( ) read as (factorial ) represents the product of first ‘ ’ natural numbers.

i.e .

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