Combinations
A combination is an unordered subset.
Contents
Counting
The number of possible combinations depends on the size of the starting set and the number taken from it. These are notated as n and k respectively.
Intuitively, there are 3 ways to take 2 from a set of 3. (A and B; B and C; A and C.) Plugging n=3 and k=2 into the equation also yields the expected result.