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 * Aim:** How do we use combinations to solve probability problems?

At the end of the lesson, you will be able to...
 * 1) define a combination
 * 2) discover a formula for the combination of n different things taken r at a time
 * 3) identify the notations used with combinations
 * 4) explain the circumstances under which a permutation should be used or under which a combination should be used
 * 5) apply the combination formula
 * 6) apply the counting principle along with combinations to count the elements in the sample space
 * 7) use a calculator to compute combinations
 * 8) use calculators to solve probability problems

Copy these questions down into your notebook. Answer them as you watch the video.
 * 1) What is a combination? Does order matter?
 * 2) How is a combination differ from a permutation?
 * 3) How do you know when to use a permutation or a combination when solving a problem?
 * 4) What are the three ways to write a combination? Which way should you write to enter the data into a graphing calculator?
 * 5) How can you use the graphing calculator to find a combination?

media type="youtube" key="SGn1913lOYM" width="425" height="350"
 * Video**

media type="youtube" key="uATuM3ajhBw" width="425" height="350"
 * Video**

1. How many different combinations of five letters can be selected from the alphabet? (Ans: 26C5 = 65780) 2. How many different combinations of 5 letters can be drawn from the alphabet if 3 are consonants and 2 are vowels? (21C3 x 5C2 = 13300)
 * Classwork:** solve the following problems:


 * Homework: #**3- 57 odd

[|Perm_and_Com_1.JPG]

[|Perm_and_Com_2.JPG]


 * Answers:**

[|A-Perm_and_com.JPG]


 * Journal entry:** The lock on your locker is probably called a combination lock. It needs a sequence of numbers rather than a key to open it. Is the word "combination" an appropriate description of would "permutation" lock be a more mathematically correct name? Explain