If the sequence of the digits is important ... 1-2-3 and 3-2-1 are different ...
then there are 10*9*8 = 720 of them.
If the sequence doesn't matter ... 1-2-3 and 2-3-1 and 3-1-2 are all the same ...
then there are only 720/6 = 120 because 3 things can be ordered 1*2*3 = 6 ways.
6
10 to the third assuming zero is included and can lead, otherwise 9 to the third, ie 729. This all assumes that you are talking about 3-digit numbers. * * * * * No. That may be the number of permutations but those are different from combinations. In a combiation, the order of the digits does not matter so that 123 is the same as 132 or 213 etc. With repetition, there are 210 COMBINATIONS, including one that is {0,0,0}.
Only one.
10
Six combinations: 123, 132, 213, 231, 312, 321
If you allow digits to be repeated (for example, 222 or 992), then there are 9 x 9 x 9 = 729 combinations. If you do not allow digits to be repeated, then there are 9 x 8 x 7 = 504 combinations.
Oh, dude, you're hitting me with some math vibes here. So, if you have 6 digits to choose from to make a 4-digit combination, you can calculate that by using the formula for permutations: 6P4, which equals 360. So, like, you can make 360 different 4-digit combinations from those 6 digits. Math is wild, man.
If no digit can be repeated then there are 5 combinations, abcd, abce, abde, acde and bcde. If you regard abdc as different from abcd then each of the 5 basic sets could be arranged 24 ways and the total would be 120 combinations.
9
45
10,000.
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).
104 = 10000 if digits can be repeated, 5040 if not. The above answers assume a code can start with a 0. If not, 9000 if digits can be repeated and 4536 if not.
45 In combinations, the order of the digits does not matter so that 12 and 21 are considered the same.
6
10 to the third assuming zero is included and can lead, otherwise 9 to the third, ie 729. This all assumes that you are talking about 3-digit numbers. * * * * * No. That may be the number of permutations but those are different from combinations. In a combiation, the order of the digits does not matter so that 123 is the same as 132 or 213 etc. With repetition, there are 210 COMBINATIONS, including one that is {0,0,0}.
Only one.