Question

Permutations acellus How many ways can 4 books be arranged on a shelf if there are 8 books to chose from? Note: nPr = n! —— (n-r)!

Answer 1

1680 ways

Explanation:

From the question,

nPr = n!/(n-r)!.................. Equation 1

Where, n = Total number of books to chose from, r = number of books to be arranged in the shelf.

Given: n = 8 books, r = 4 books.

Substitute into equation 1

8P4 = 8!/(8-4)!

8P4 = 8!/4!

8P4 = (8×7×6×5×4!)/4!

8P4 = 1680 ways.

Hence the number of ways 4 books can be arranged in a shelf if there are 8 books to chose from is 1680 ways