Question 1204860
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The wording of your post leaves open the possibility of very different interpretations of the problem.<br>
(a) 4 books on the shelf vertically can be arranged in 4! = 24 different ways.<br>
(b) 6 books in a pile can be arranged in 6! = 720 different ways.<br>
(c) The 10 books together, 4 vertically and 6 in a pile, can be arranged in 24*720 = 17280 different ways.<br>
If the intended problem involves which of the 11 books are stored vertically or in the pile, then of course that is a completely different problem.<br>
If my answers are not what you expected, then re-post the problem, defining it clearly....<br>