That depends upon whether you are allowed to repeat numbers. If you are allowed to repeat, that means that all seven digits (say 1 through 7) can be used in each of the four positions of your...
8x7x6x5x4x3x2 or 40320* * * * *That is totally incorrect. There are only 8 combinations: one with each of the 8 numbers missing. In a combination the order does not matter so 1234567 is the same as...
If repetition is allowed and order is important, then you have essentially a base-4 number system, with the numbers ranging from 00004 to 33334. The quantity of permutations in this example is 44 =...