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ANSWER. 9*8*7*6*5 = 15120 different arrangements.
The product of 5 consecutive integer numbers in the descending order, starting from 9.
Explanation
Any of 9 books in the first position.
Any of remaining 8 books in the next position.
. . . and so on . . .
Solved and explained.
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See the lesson
- Special type permutations problems
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Free of charge online textbook in ALGEBRA-II
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