Lesson 7 of 15Article18 min
Ch 6 — Permutations and Combinations
Fundamental principle of counting → permutations (order matters) → combinations (order does not). This chapter feeds binomial theorem and probability.
01Counting with order and without
Fundamental principle of counting → permutations (order matters) → combinations (order does not). This chapter feeds binomial theorem and probability.
- Factorials: n! = n·(n−1)·…·1; 0! = 1.
- Distinguish arrangements of letters with repeats.
- Circular permutations: (n−1)! for distinct objects in a circle (standard NCERT case).