How can I double check my math answers?

Resolve equations using alternative methods (e.g., check quadratic roots by plugging them back into ax² + bx + c), verify decimals using scientific solvers, and review step-by-step worked calculations.

Where are these syllabus concepts applied in real life?

Trigonometry is used in architecture, mechanics and navigation. Quadratic equations model rocket trajectories and profit boundaries. Basic arithmetic and fractions are applied in accounting, budgeting and lab chemistry.

Back to Class XI Mathematics

Class XI Mathematics

Chapter 6: Permutations and Combinations

Standard NCERT & CBSE aligned study curriculum. Master concepts, track accuracy, revise weak areas, and challenge yourself with 9 customized practice modes.

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Syllabus Sections

Key Formulas & Equations

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Permutations nPr

^nP_r = \frac{n!}{(n-r)!}

Arrangements of n items taken r at a time.

Combinations nCr

^nC_r = \frac{n!}{r!(n-r)!}

Selections of n items taken r at a time.

Related Formulas from Adjacent Chapters

Inequality sign multiplication

a < b \land c < 0 \Rightarrow ac > bc

[From Linear Inequalities] Reverses inequality sign when multiplying by a negative number.

Binomial Theorem

(a+b)^n = \sum_{r=0}^{n} ^nC_r a^{n-r} b^r

[From Binomial Theorem] Expands binomial to the n-th power.

General Term of Expansion

T_{r+1} = ^nC_r a^{n-r} b^r

[From Binomial Theorem] Calculates the (r+1)th term of binomial expansion.