### Mathematics Class XI

Unit-I: Sets and Functions
Chapter 1: Sets
Unit-II: Algebra
Chapter 5: Binomial Theorem
Chapter 6: Sequence and Series
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

# Combination

In a combination order is not important. We are selecting objects in different ways.

It is denoted by or . . . . . . If . . . . The number of non-negative solutions of the equation is given by or . No. of combinations when ‘ ’ particular things are always included . No. of ways of selecting zero or more things out of ‘ ’ identical things is . Number of circular arrangement of things is . Number of circular permutations of dissimilar things taken at a time  The number of ways on which ‘ ’ things can be distributed among two persons, one receives ‘ ’ and another receives thing s-t . If we want to keep the things in two heaps then the number of selection . If we want to keep identical things in 3 heaps then no. of selection . If things are to be divided equally among three people, then the no. of ways . No. of ways in which different things can be divided into three different groups containing respectively is .

Dearrangements :

No. of ways in which ‘ ’ letters can be put in corresponding envelopes s-t no letter goes to correct envelope is .

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