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How many ways can a librarian arrange 15 books on a top shelf if she has 20 books from which to pick?
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How many ways can a librarian arrange 15 books on a top shelf if she has 20 books from which to pick?

User Yuriy Zaletskyy
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2 Answers

4 votes

20\cdot19\cdot\ldots\cdot7\cdot6=20,274,183,401,472,000
User Intraector
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1 vote

Answer: 20!/5!

Explanation:

User Aleadam
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