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On my bookshelf I have 5 books of poetry, 15 graphic novels, 8 biographies and 3 self-help books.
I plan to take 7 books with me on my vacation.
a)In how many different ways can I take 7 books with me on my vacation?
b)In how many different ways can my 7 books consist of 2 books of poetry, 3 graphic novels and 2 self-help books?
c)In how many different ways can my 7 books consist of exactly 3 graphic novels?
d)In how many different ways can my 7 books consist of at least 6 biographies?
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(b) In how many different ways can my 7 books consist of 2 books of poetry, 3 graphic novels and 2 self-help books?
You can select 2 books of poetry from 5 books of poetry by = = 10 ways.
You can select 3 graphic novels from 15 graphic novels by = = 455 ways.
You can select 2 self-help books from 3 self-help books by = = 3 ways.
Since these selections are INDEPENDENT in separate categories, the total number of choices is the product 10*455*3 = 13650,
according to the foundamental counting principle.
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On Combinations, see introductory lessons
- Introduction to Combinations
- PROOF of the formula on the number of Combinations
- Problems on Combinations
- Fundamental counting principle problems
- OVERVIEW of lessons on Permutations and Combinations
in this site.
Also, you have this free of charge online textbook in ALGEBRA-II in this site
- ALGEBRA-II - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this online textbook under the topic "Combinatorics: Combinations and permutations".
Save the link to this textbook together with its description
Free of charge online textbook in ALGEBRA-II
https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson
into your archive and use when it is needed.