<h3>Answer:</h3>
There are 40,320 ways, in which 8 books can be arranged on a shelf.
<h3>Solution:</h3>
Here, we are to find the number of ways in which 8 books can be arranged on a shelf. The total number of books is 8 and the way of arranging books is also 8.
- If one book is placed in the first place, then 7 books will be placed in front of it. If 2 books are placed in the 2nd place, then only 6 books can be placed after that book. This sequence will continue till 1 .
<u>Permutations </u><u>:</u>
- A permutation is an arrangement of objects in a definite order.
➲<u> P ( n, r )= n ! / ( n - r ) !</u>
- n = total number of objects
- r = number of objects selected
The number of ways to arrange 8 books on a shelf will be :
➝ P ( n, r ) = n ! / ( n - r ) !
➝ P ( n, r ) = 8 ! / ( 8 - 8 ) !
➝ P ( n, r ) = 8 ! / 0 !
➝ P ( n, r ) = 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1 / 1
➝ P ( n, r ) = 40, 320
ㅤㅤㅤㅤㅤㅤ~ Hence, there are <u>40,320 ways</u> in which 8 books can be arranged on a shelf !
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