Question

The numbers 0 through 9 are used in code groups of four to identify an item of clothing. code 1083 might identify a blue blouse, size medium. the code group 2031 might identify a pair of pants, size 18, and so on. repetitions of numbers are not permitted—in other words, the same number cannot be used more than once in a total sequence. as examples, 2,256, 2,562, or 5,559 would not be permitted. how many different code groups can be designed?

Answer 1

The first digit can be any of 10; the next, any of 9; the 3rd digit can be any of 8; and the last digit can be any of 7.
.. 10*9*8*7 = 5040 . . . . different code groups