In how many ways can 3 books be arranged on a shelf if there are 5 books to choose from?

Answer 1

This is an example of a permutation, because the order of the books matters. If the order didn't matter, it would be a combination.

The formula for the number of permutations of n objects taken r at a time is given by this formula:

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

where ! is the factorial operator. In our example, n=5 and r=3, so we have:

P(5,3) = 5!/(5-3)!

= 5!/2!

= 5*4*3*2*1/2*1

= 5*4*3

= 60