If all numbers can be used as many times as wanted then there are 109 = one billion combinations. If each number can be used only once, there are 10!/(10-9)! = 10!/1! = 10! = 3628800 combinations.
* * * * *
Clearly answered by someone who does not know the difference between PERMUTATIONS and COMBINATIONS.
The combination 123456789 is the same as the combination 213456789 etc.
All in all, therefore, there are only ten combinations which use each digit at most once.
In California, for example, the first digit of a standard plate is a number, followed by 3 letters, and then three numbers. There are 26 letters in the alphabet, so there are 26 raised to the 3rd power combinations, or 26 * 26 * 26, which is 17,576 possibilities just of the 3 letters.
10 digit numbers
Commonly there are 16 numbers in a credit card. The first digit is the major industry identifier and the first 6 digits including the major industry identifier are the issuer identifier numbers and the last digit is the check digit.
The structure of the card number varies by system. For example, American Express card numbers start with 37; Carte Blanche and Diners Club with 38.American Express - Digits three and four are type and currency, digits five through 11 are the account number, digits 12 through 14 are the card number within the account and digit 15 is a check digit.Visa - Digits two through six are the bank number, digits seven through 12 or seven through 15 are the account number and digit 13 or 16 is a check digit.MasterCard - Digits two and three, two through four, two through five or two through six are the bank number (depending on whether digit two is a 1, 2, 3 or other). The digits after the bank number up through digit 15 are the account number, and digit 16 is a check digit.
that question cant be answered unless it was 3 odd-digits or 4 odd-digits with 1 even digit i think.
45.
This question needs clarificatioh. There are 4 one digit number combinations, 16 two digit combinations, ... 4 raised to the n power for n digit combinations.
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.
Number of 7 digit combinations out of the 10 one-digit numbers = 120.
99. Each of the numbers in the list can only be used by itself otherwise you would get a 4-digit (or longer) number.
Exactly 3,628,800, or 10!.
There are 38760 combinations.
It is: 9C7 = 36
66
10,000
15
10!/3! = 604800 different combinations.