Explanation
The question wants us to determine the number of different ID cards that can be made if there are 3 digits on a car.
To do so, let us first list out all the possible outcomes. These are:
[tex]0,1,2,3,4,5,6,7,8,9[/tex]
We can see that there are 10 possible digits
For the first case where no digit can be used more than once, we will have
Therefore, there are
[tex]10\times9\times8=720\text{ ID cards}[/tex]
For the second case, if the digits can be repeated, then, we will have
Then, since the numbers can be repeated, we will have
[tex]10\times10\times10=1000\text{ ID cards}[/tex]
