1. Chapter 12: Rational Expressions & Functions 12.8 Combinations

2. Permutations vs Combinations Permutations have a specific order – My sandwich needs to be bread, cheese, meat, bread Combinations can be any order – My sandwich can be in any order, just has to have two slices of bread, meat, and cheese

3. Finding Combinations

4. Example 1

5. Example 2 Twenty people report for jury duty. How many different twelve-person juries can be chosen?

6. Example 2a For your history report, you can choose to write about two of a list of five presidents of the United States. Find the number of combinations possible for your report. Explain why you should model this situation with combinations, not permutations.

7. Example 3 Suppose you have six new CDs (two rock, two R&B, and two jazz) to put on a rack. If you choose the CDs are random, what is the probability that the first one is jazz and the second one is R&B?

8. Example 3a Suppose you have three novels and two history books to read over the summer. If you choose these books at random, what is the probability that you first choose a novel, and then a history book?

9. Rewrite probability as combinations

10. Example 4 Suppose you have six Virginia quarters and four Connecticut quarters in a change purse. You choose three quarters without looking. What is the probability that all the quarters you choose are Virginia quarters?

11. Example 4a Suppose you have the quarters in Example 4. You choose four quarters at random. How many combinations are possible? How many combinations are only Connecticut? What is the probability that all of the quarters are Virginia?

12. Homework P. 709 2-20 even, 24, 26, 30