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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? 20!/5! 20!/15! 15!/5!

How many ways can a librarian arrange 15 books on a top shelf if she has 20 books from which to pick? 20!/5! 20!/15! 15!/5!
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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?

20!/5!
20!/15!
15!/5!

User Stereoputrid
by
8.2k points

2 Answers

6 votes
The correct answer is A turned this in got a 100 hoped this helped ya.
User Midnight Guest
by
8.8k points
3 votes
Use the permutation formula
nPr = (n!)/((n-r)!)
20P15 = (20!)/((20-15)!)
20P15 = (20!)/(5!)

The final answer is choice A

User Magmatic
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8.5k points
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