9. Additional Topics in Probability and Counting
Applications of Counting Principles
Editor's Notes
the Fundamental Counting Principle is used to find the number of ways two or more events can occur in sequence. An important
application of the Fundamental Counting Principle is determining the number of ways that n objects can be arranged in order. An ordering of n objects is called
a permutation.
You may want to choose some of the objects in a group and put them in order. Such an ordering is called a permutation of n objects taken r at a time.
You can think of a combination of n objects chosen r at a time as a permutation of n objects in which the r selected objects are alike and the
remaining n - r (not selected) objects are alike.