SOLUTION: How many four digit numbered license plates can be made such that NO two plates are identical?

These are the whole numbers from 1000 through 9999.

There are 9999 whole number from 1 through 9999, inclusive.
But the 999 whole numbers from 1 through 999 can't be used
since they don't have 4 digits. So the answer is:

9999
-999
----
9000

Another way to do it is this way:

There are 10 digits, 1,2,3,4,5,6,7,8,9,0

Choose the first digit 9 ways (can't use 0)
Choose the second digit 10 ways (can be 0)
Choose the third digit 10 ways (can be 0)
Choose the fourth digit 10 ways (can be 0)

Answer: (9)(10)(10)(10) - 9000

Edwin