How many ways can 7 books be arranged on a shelf 5 at a time

Solution:

Given, 7 books arranged on a shelf 5 at a time.

We have to find the possible number of ways of arranging the books.

By permutation,

P(n,r) = n!/(n - r)!

Here, n = 7 and r = 5

P(7,5) = 7!/(7 - 5)!

= 7!/2!

= (7 × 6 × 5 × 4 × 3 × 2 × 1)/(2 × 1)

= 7 × 6 × 5 × 4 × 3

= 42 × 60

= 2520

Therefore, the books can be arranged in 2520 ways.

How many ways can 7 books be arranged on a shelf 5 at a time

Summary:

7 books can be arranged on a shelf 5 at a time in 2520 ways.