Question

If no digit may be used more than once, how many 5-digit numbers can be formed using only the digits 3, 8, 1, 2, 5, and 7?

Answer 1

The number of permutations of
`m(0\leq m\leq n)` objects from n objects is


`P(m,n)=(n!)/((n-m)!)`

Here 5 digits are chosen from 6 digits without replacement (order important).

The number of 5 digit numbers that can be formed is

`(6!)/((6-5)!) =6!=720`