Use factorials to solve this problem.
When you are choosing a number of digits from a set without repetition, you will use the following formula:
![(n!)/((n-r)!)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/8zsn91wmxw9lwnchb1goz7xr5yzz82fld3.png)
n represents the total amount of items in the set, and r represents the number of items you will take out.
There are 10 digits, and you are choosing sets of 6 digits for your code. Plug the values into the equation:
![\text{n = 10, r = 6}](https://img.qammunity.org/2019/formulas/mathematics/middle-school/qwnkl49mnp8uw303xm7q2zzbio7w42ovb5.png)
![(10!)/((10-6)!) = (10!)/(4!) = \boxed{151,200}](https://img.qammunity.org/2019/formulas/mathematics/middle-school/jo73zpmz8deiwqbcjshlyxcofy17le4s6e.png)
There are
151,200 different 6-digit codes possible.