6
Six combinations: 123, 132, 213, 231, 312, 321
Not repeating, it is 7*6*5*4 which is 840 ways ---- There are 7 choices for each of four digits, right? 74 = 2401
120 combinations using each digit once per combination. There are 625 combinations if you can repeat the digits.
How many license plates can be made using either two uppercase English letters followed by four digits or two digits followed by four uppercase English letters?
45
6
32C3 = 4960
Six combinations: 123, 132, 213, 231, 312, 321
Assuming you are treating each number as a number and not as an individual unit, the numbers you can make from these digits are 899, 989 and 998.
Not repeating, it is 7*6*5*4 which is 840 ways ---- There are 7 choices for each of four digits, right? 74 = 2401
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.
3 x 3 x 3 x 3 = 81 combinations
94
I assume you mean how many 4-digit numbers can be made from a set such as {A,A, B, C} where A, B and C are single digits. There are 12 such numbers.
120 combinations using each digit once per combination. There are 625 combinations if you can repeat the digits.
017, 071, 107, 170, 701, 710. 6 combinations