There are 210 4 digit combinations and 5040 different 4 digit codes.
Any 4 from 10 in any order = 10 x 9 x 8 x 7 = 5040
There are 4 possible numbers if the digits are not repeated; 18 if they are. Those are 3-digit numbers, assuming that zero would not be a leading digit. If zero is allowed for a leading digit, then you can have 6 for the non repeated, and 27 if repetition.
10,000
There are seven possible digits for the first digit and 6 digits for the second (minus one digit for the digit used as the first digit) and 5 options for the last digit (minus one again for the second digit) and then you just multiply them all together to get a total possible combination of 210 numbers that are possible.
There are 210 4 digit combinations and 5040 different 4 digit codes.
There are 10000 such codes. Each of the numbers 0-9 can be in the first position. With each such first digit, each of the numbers 0-9 can be in the second position. With each such pair of the first two digits, each of the numbers 0-9 can be in the third position. etc.
Any 4 from 10 in any order = 10 x 9 x 8 x 7 = 5040
1,000 of them. The list of possibilities will look exactly like the counting numbers from 000 to 999 .
1000
There are 4 possible numbers if the digits are not repeated; 18 if they are. Those are 3-digit numbers, assuming that zero would not be a leading digit. If zero is allowed for a leading digit, then you can have 6 for the non repeated, and 27 if repetition.
The possible 4 digit codes using the numbers 0-9 are every number between 0 and 9999. For numbers that have less than 4 digits, just precede the number with 0's. 10,000 possibilities
Total number of possible 3-digit numbers = 9!x10!10!
10,000
103 = 1000 in all.
9999999999 100000000
Using the digits of 1345678, there are 210 three digit numbers in which no digit is repeated.