There are 38760 combinations.
Number of 7 digit combinations out of the 10 one-digit numbers = 120.
The answer will depend on how many digits there are in each of the 30 numbers. If the 30 numbers are all 6-digit numbers then the answer is NONE! If the 30 numbers are the first 30 counting numbers then there are 126 combinations of five 1-digit numbers, 1764 combinations of three 1-digit numbers and one 2-digit number, and 1710 combinations of one 1-digit number and two 2-digit numbers. That makes a total of 3600 5-digit combinations.
It is: 9C7 = 36
There are 1140 five digit combinations between numbers 1 and 20.
10!/3! = 604800 different combinations.
that would be 9 to the 7th power i believe.
There are 840 4-digit combinations without repeating any digit in the combinations.