A combination is a selection of elements from a set where the order in which they are selected is not important. Therefore, the only important thing is which elements are selected. For example, choosing two different ingredients for a salad from five unique options in the salad bar.
When counting the number of possible combinations, either:
This formula calculates the number of combinations that can be done by using elements of a set to form groups of elements. Note that the exclamation points in the formula indicate that the factorial of the value should be calculated.
In the salad bar example, there were options provided to make groups of
An alternate notation for is