3x10x10x10x9=2700
For a four-digit ID code, you would have 10x10x10x10, so 10000 different codes. With a five-digit and one letter ID code, you have 10x10x10x10x10x26 or 2,600,000 different codes. So there are 2,600,000-10,000 more, or 2,590,000 more codes.
> 9999876 Actually, 9999876 has four different digits (6, 7, 8, 9). The largest 7-digit number with three different digits is 9999987.
Since there are only five different digits, a 6-digit number can only be generated if a digit can be repeated. If digits can be repeated, the smallest 6-digit number is 111111.
123
The number of 3-digit numbers with no repeated digits is simply 10x9x8 = 720, if you allow, for example, 012 as a 3-digit number. There are 10 digits, any of which might be the first digit. The second digit can be any digit except the digit that was used for the first digit, leaving 9 possibilities. The third digit then has 8 possibilities, since it can't be the same as the first or second digit. The actual number of possible area codes will be lower, because there are additional restrictions on the number combinations for a valid area code. For example, in North America (USA, Canada, etc.), the first digit of an area code cannot be 0 or 1 and the middle digit cannot be 9.
If you include 0000, ten thousand unique four digit codes are possible.
10*9*8*7*6=30,240
As far as I can tell, all 5 digit numbers are potential zip codes, so there are 99999 + 1 potential zip codes, or 100,000. Many of these are not actually is use.
There can be 103 = 1000 codes.
There are 210 4 digit combinations and 5040 different 4 digit codes.
1000
9,876
10,000
9876 (:
There are 2 possible digits for the first digit (3 or 4), leaving 3 possible digits for the second digit (5 and 6 and whichever was not chosen for the first), leaving 2 possible digits for the third. Thus there are 2 × 3 × 2 = 12 possible 3 digit numbers.
900 ,999 ,909
10!/(10-6)! =10!/4! = 10*9*8*7*6*5 = 151200 different codes