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a science teacher is arranging her books on a shelf. she has 4 astrology books, 3 biology books, and 2 chemistry books. how many ways can she arrange these books on the shelf if the books from each subject must be put together?

 May 27, 2021
 #1
avatar+7 
+3

Let AAAA be the 4 astronomy books, BBB be the biology books, and CC be the chemistry books. We can group the terms into X, Y, Z repsetivley. Hence we get:

 

XYZ

 

There are 3! ways to rearrange this. However, each of the X can be rearranged 4! ways, and the Y can be rearranged in 3! ways, and the Z can be rearragned in 2! ways.

 

Hence, our answer is:

 

4! * 3! * 3! * 2!

 

1728

 May 27, 2021
edited by danielyskim1119  May 27, 2021
 #3
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+1

god thank you so much

Guest May 27, 2021
 #2
avatar+114069 
+1

 

Give yourself a point Daniel  cool

 May 27, 2021

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