There can be 103 = 1000 codes.
If you include 0000, ten thousand unique four digit codes are possible.
If the first digit can be zero, there are 5,040. If the first digit can't be zero, there are only 4,536.
this is impossible
10!/(10-6)! =10!/4! = 10*9*8*7*6*5 = 151200 different codes
There are 210 4 digit combinations and 5040 different 4 digit codes.
There can be 103 = 1000 codes.
If you include 0000, ten thousand unique four digit codes are possible.
If the first digit can be zero, there are 5,040. If the first digit can't be zero, there are only 4,536.
104 or 10000
3x10x10x10x9=2700
There are no ten digit zip codes. Maryland has many five digit zip codes and many many more nine digit zip+4 codes. There can be a unique nine digit zip+4 code for every mailbox in a post office building and for at least every block in a town or city!
I would have to say 10,000 possible combinations. (0000, 0001, 0002 through 9998, 9999)
-4
this is impossible
10!/(10-6)! =10!/4! = 10*9*8*7*6*5 = 151200 different codes
4+4+4+4+4= 20