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MATH104 Ch. 11: Probability Theory. Permutation Examples. 1. If there are 4 people in the math club ( A nne, B ob, C indy, D ave), and we wish to elect a president and vice-president, LIST all of the different ways that this is possible.
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Permutation Examples 1. If there are 4 people in the math club (Anne, Bob, Cindy, Dave), and we wish to elect a president and vice-president, LIST all of the different ways that this is possible. 2. From these 4 people (Anne, Bob, Cindy, Dave), we wish to elect a president, vice-president, and treasurer. LIST all of the different ways that this is possible.
Answers 1. If there are 4 people in the math club (Anne, Bob, Cindy, Dave), and we wish to elect a president and vice-president, LIST all of the different ways that this is possible. AB BA CA DA AC BC CB DB AD BD CD DC 4*3=12 or 4P2 = 12
Answers 2. From these 4 people (Anne, Bob, Cindy, Dave), we wish to elect a president, vice-president, and treasurer. LIST all of the different ways that this is possible. ABC ABD…
A B C ABC D ABD C B ACB D ACD D A BDA C BDC • B A C BAC D BCD C A BCA D BCD D A BDA C BDC • C A B CAB D CAD B A CBA D CBD A B DAB C DAC • D A B DAB C DAC B A DBA C DBC C A DCA B DCB 4*3*2 = 24 outcomes Or 4P3 = 24
More counting examples: 1. At a restaurant, you have a choice of main dish (beef, chicken, fish, vegetarian), vegetable (broccoli, corn), potato (baked, fries), and dessert (chocolate, strawberry). LIST all possible choices.
2. T/F quiz 2. A teacher wishes to make all possible different answer keys to a T/F quiz to cut down on cheating. How many possible different answer keys could there be if there are 4 questions. LIST them all.
3. T/F test 3. What if there were 10 T/F questions. Just explain (do not list).
4. Multiple choice test 4. A teacher wishes to make all possible different answer keys to a multiple choice quiz. How many possible different answer keys could there be if there are 3 questions that each have 4 choices (A,B,C,D). LIST them all.
5. And 6. 5. What if there were 20 multiple choice questions with 5 choices each? Explain (don’t list). 6. With 9 baseball players on a team, how many different batting orders exist?
Counting Rules Fundamental Counting/ –Multiplication Rule (p. 608) If you can choose one item from a group of M items and a second item from a group of N items, then the total number of two-item choices is M*N. Permutation of n things taken r at a time (p. 617) nPr = n!/(n-r)! Question: In permutations, does ORDER matter? Is REPITITION allowed? Permutations of Duplicate items (p. 618) The number of permutations of n items, where p items are identical, q items are identical, r items are identical, and so on, is given by
More multiplication and permutation problems 1. With 14 players on a team, how many ways could we pick a batting order of 11? 2. If license plates have 3 letters and then 4 numbers, how many different license plates exist?
3 3. A stock can go up, down, or stay unchanged. If you own 7 stocks, how many different possibilities are there?
4 4. How many different four-letter radio station call letters can be formed if the first letter must be W or K? 5. A social security number contains nine digits. How many different ones can be formed?
6 6. If you wish to arrange your 7 favorite books on a shelf, how many different ways can this be done? 7. If you have 10 favorite books, but only have room for 7 books on the shelf, how many ways can you arrange them?
8 8. You wish to arrange 12 of your favorite photographs on a mantel. How many ways can this be done? 9. You have 20 favorite photographs and wish to arrange 12 of them on a mantel. How many ways can that be done?
10. 10. You take a multiple choice test with 12 questions (and each can be answered A B C D E). How many different ways could you answer the test?
11. How many ways can you rearrange the letters in a. CAT? b. OHIO? c. CLASSES? d. MISSISSIPPI?
12 12. If a station plans on running 6 (identical) Democratic ads, 6 (identical) Republican ads, and 4 (identical) Independent ads, in how many ways can they order these? 13. If you saw 15 movies last year, how many ways can the top 3 be chosen and ranked?
14 14. 20 people purchase raffle tickets. How many ways could we award a 1st, 2nd, and 3rd prize. 15. You have 50 different outfits. How many ways can you pick your first and second favorite? How about your first, second, and third favorite?
Combination Questions • If there are 4 people in the math club (Anne, Bob, Cindy, Dave), and 2 will be selected to attend the national math conference. LIST all of the different ways that this is possible. • From these 4 people (Anne, Bob, Cindy, Dave), and 3 will be selected to attend the national math conference. LIST all of the different ways that this is possible.
Combination answers 1. If there are 4 people in the math club (Anne, Bob, Cindy, Dave), and 2 will be selected to attend the national math conference. LIST all of the different ways that this is possible. AB AC BC AD BD CD 4C2= 6
Combination answer 2. From these 4 people (Anne, Bob, Cindy, Dave), and 3 will be selected to attend the national math conference. LIST all of the different ways that this is possible. ABC BCD ABD ACD 4C3 = 4
Permutations and Combinations • Permutations • Use when ORDER matters and NO repitition • nPr = n!/(n-r)! • Example: If 10 people join a club, how many ways could we pick pres and vp? 10P2 = 90 • Combinations • Use: ORDER does NOT matter and NO repitition • nCr = n!/ [(n-r)!r!] • Example: 10 people join a club. In how many ways could we pick 2? 10C2 = 45
Combination of n things taken r at a time (p. 623) Use the combination formula nCr = n!/[(n-r)!r!] to answer these combination problems 1. If there are 20 people on a committee, how many ways could we pick a subcommittee of 7 of them? 2 If there are 100 senators, how many ways could we pick a subcommittee of 7 of them? 3 If there are 72 potential jurors, how many different ways could they pick a jury of 12?
Decide and answer: Combination, permutation, or multiplication? • There are 8 possible pizza toppings. How many ways could we pick 3 toppings? 2 . 20 people apply for a scholarship. 3 are chosen. In how many ways can they be chosen? 3. 32 people are in a class where the teacher plans on awarding 4 A’s. If all possibilities were written out, how many would there be?
Change some of the following permutation problems into combination problems 1. Permutation question: With 14 players on a team, how many ways could we pick a batting order of 11? Answer: 14P11 Write a combination questions whose answer is 14C11 2. Permutation question: If you have 10 favorite books, but only have room for 7 books on the shelf, how many ways can you arrange them?Answer: 10P7 Write a combination questions whose answer is 10C7
… 3. Permutation question: You have 20 favorite photographs and wish to arrange 12 of them on a mantel. How many ways can that be done? Answer: 20P12 Write a combination questions whose answer is 20C12 4. Permutation question: If you saw 15 movies last year, how many ways can the top 3 be chosen and ranked? Answer: 15P3 Write a combination questions whose answer is 15C3
5. Permutation question: 20 people purchase raffle tickets. How many ways could we award a 1st, 2nd, and 3rdprize.Answer: 20P3 Write a combination questions whose answer is 20C3
More challenging combination problems 1 If we have 4 teachers and 7 students and wish to form a committee of 2 teachers and 3 students, in how many different ways can this be done?
… 2 . A test has 5 essay questions and 10 short answer questions. A student is to select to answer 3 essay questions and 7 short answers. In how many different ways could this be done?
Multiplication Problems 1. At a restaurant, you have a choice of main dish (beef, chicken, fish, vegetarian), vegetable (broccoli, corn), potato (baked, fries), and dessert (chocolate, strawberry). LIST all possible choices. 2. A teacher wishes to make all possible different answer keys to a multiple choice quiz. How many possible different answer keys could there be if there are 3 questions that each have 4 choices (A,B,C,D). LIST them all. 3. What if there were 20 multiple choice questions with 5 choices each? Explain (don’t list). 4. With 9 baseball players on a team, how many different batting orders exist?
Answers 1. At a restaurant, you have a choice of main dish (beef, chicken, fish, vegetarian), vegetable (broccoli, corn), potato (baked, fries), and dessert (chocolate, strawberry). LIST all possible choices. main vegetable potato dessert
Answers 2. A teacher wishes to make all possible different answer keys to a multiple choice quiz. How many possible different answer keys could there be if there are 3 questions that each have 4 choices (A,B,C,D). LIST them all. 3. What if there were 20 multiple choice questions with 5 choices each? Explain (don’t list). 4. With 9 baseball players on a team, how many different batting orders exist?
Multiplication, Permutation, or Combination? 1. With 14 players on a team, how many ways could we pick a batting order of 11? 2. If license plates have 3 letters and then 4 numbers, how many different license plates exist? 3. How many different four-letter radio station call letters can be formed if the first letter must be W or K? 4. A social security number contains nine digits. How many different ones can be formed? 5. If you wish to arrange your 7 favorite books on a shelf, how many different ways can this be done?
6. If you have 10 favorite books, but only have room for 7 books on the shelf, how many ways can you arrange them? 7. You wish to arrange 12 of your favorite photographs on a mantel. How many ways can this be done? 8. You have 20 favorite photographs and wish to arrange 12 of them on a mantel. How many ways can that be done? 9. You take a multiple choice test with 12 questions (and each can be answered A B C D E). How many different ways could you answer the test? 10. If you had 13 pizza toppings, how many ways could you pick 5 of them?