If the 6 digits can be repeated, there are 1296 different combinations. If you cannot repeat digits in the combination there are 360 different combinations.
* * * * *
No. That is the number of PERMUTATIONS, not COMBINATIONS.
If you have 6 different digits, you can make only 15 4-digit combinations from them.
about 1,0000000000000
10C6 = 10*9*8*7/(4*3*2*1) = 210 combinations.
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.
Each digit can appear in each of the 4 positions. There are 9 digits, therefore there are 9⁴ = 6561 such combinations.
There are infinite combinations that can make 3879
Only one.
45 In combinations, the order of the digits does not matter so that 12 and 21 are considered the same.
about 1,0000000000000
9,000 - all the numbers between 1,000 and 9,999 inclusive. * * * * * NO. Those are PERMUTATIONS, not COMBINATIONS. Also, the question specified 4 digit combinations using 4 digits. The above answer uses 10 digits. If you start with 4 digits, you can make only 1 combination.
120 combinations using each digit once per combination. There are 625 combinations if you can repeat the digits.
10C6 = 10*9*8*7/(4*3*2*1) = 210 combinations.
Only one: 2468. The order of the digits in a combination does not make a difference.
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.
There are 167960 9 digits combinations between numbers 1 and 20.
Each digit can appear in each of the 4 positions. There are 9 digits, therefore there are 9⁴ = 6561 such combinations.
There are infinite combinations that can make 3879
Allowing repetitions, there are 9 combinations. Without repeated digits, there is only one combination of 3 digits from 3.