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I'm confused on these arrangement problems:

 

9 different books are to be arranged on a bookshelf. 4 of these books were written by Shakespeare, 2 by Dickens, and 3 by Conrad. How many possible permutations are there if the books by Conrad must be separated from one another?

 Jun 24, 2020
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Total possible arrangements for the six books: 6! or 720

 

Places for Conrad's books are:

First book: 7 possible places

Second book: 6 possible places

Third book: 5 possible places

 

If we multiply that together, we'll get the total number of permutations! 

 

So, our answer is 720 * 7 * 6 * 5 or 151200.

 
 Jun 24, 2020

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