Yuo can make only one combination of 30 digits using 30 digits.
9
12, including a combination containing 0 digits.
If you use each number once, there are six combinations.
The order of the digits in a combination does not matter. So 123 is the same as 132 or 312 etc. There are 10 combinations using just one of the digits (3 times). There are 90 combinations using 2 digits (1 once and 1 twice). There are 120 combinations using three different digit. 220 in all.
Assuming the digits cannot be repeated, there are 7 combinations with 1 digit, 21 combinations with 2 digits, 35 combinations with 3 digits, 35 combinations with 4 digits, 21 combinations with 5 digits, 7 combinations with 6 digits and 1 combinations with 7 digits. That makes a total of 2^7 - 1 = 127: too many for me to list. If digits can be repeated, there are infinitely many combinations.
All the possible digits (10 of them; 0-9) are multiplied by themselves by the number of digits that can be shown in the lock. (3) This is 103, or 1,000. This certainly shows why guessing is not a good way to break into a numerical lock, especially since three is a rather low number of digits for one!
6,720 combinations.
5040, assuming none of the digits are the same. (Assuming they're not, there's 5040 unique combinations you can make out of 7 digits).
10000
10,000.
6 for 3-digits, 6 for 2-digits, 3 for 1-digits, and 15 for all of the combinations
Since a number can have infinitely many digits, there are infinitely many possible combinations.
45
There are 167960 9 digits combinations between numbers 1 and 20.
about 1,0000000000000
Just one.