$7 \cdot 75$ A state issues license plates consisting of 6 digits (made up of the digits 0-9), and stipulates that any two license plates must differ in at least two digits (thus, the plate numbers 027592 and 020592 cannot both be used). Try to find the maximum number of license plates possible?
[Solution] We take all different 5-digit numbers (including those with 0 as the leading digit), which totals $10^{5}$. Then, the 6th digit of each license plate number is the unit digit of the sum of the first 5 digits. It is easy to verify that these $10^{5}$ numbers meet the requirements of the problem.

On the other hand, in any $10^{5}+1$ license plate numbers, there must be two numbers whose first 5 digits are the same, which of course does not meet the requirements of the problem. Therefore, the maximum number of license plates is $10^{5}$.