A112­8Combinations.notebook
January 07, 2013
Algebra 1
Ch.12 Notes Page 43
P43 12­8 Combinations
Suppose you are making a sandwich with three of these ingredients:
Turkey, Cheese, Tomato, and Lettuce.
Below are the permutations of the four ingredients listed 3 at a time.
How many different sandwiches could you really make?
A112­8Combinations.notebook
January 07, 2013
Combinations
An Arrangement of Items where ORDER IS NOT IMPORTANT
How many ways can you pick 2 out of 3 letters when order is not important from the letters A, B, C ???
Combination Calculation
n C r
n = how many things in the group.
r = how many of the things that you are picking at a time.
Start at the number n and use the first r numbers going toward zero.
Just like a Permuation.
However, you have to divide by r! to get rid of all of the duplicates.
How many ways can you pick 3 people out of 8 when Order is Not Important?
A112­8Combinations.notebook
January 07, 2013
Example
Twenty people report for jury duty.
How many differnt twelve person juries can be chosen?
Special Combinations
5 C 5 = ?
4 C 4 = ?