Combinations

Introduction

The number of k-combinations of an n-set can be expressed in terms of the number of k-permutations in that set.

• For every k-combination
• there are exactly k! permutations of its elements

k-combination of an n-set (number of permutations of n) / (number of permutations of k)

Why?

REFERENCES

Combinations. Sal Khan. Khan Academy.