counting problem 2
2012-02-28 6:30 pm
2. there are 20 different books in a row of a book shelf.How many number of ways to select 6 books such that no two books are adjacent to each other?
回答 (2)
2012-02-28 8:50 pm
✔ 最佳答案
( ) 1 ( ) 2 ( ) 3 ( ) 4 ( ) 5 ( ) 6 ( ) 7 ( ) 8 ( ) 9 ( ) 10 ( ) 11 ( ) 12 ( ) 13 ( ) 14 ( )The question is equivalent to the number of ways to insert 6 books into 15 ( ) , 15C6 = 5005 ways.
2012-02-29 12:28 am
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