### Instruction: How many possible 9-digit zip codes are possible if the first digit cannot be zero?### Response: To form a 9-digit zip code, I need to choose one digit for each of the nine positions.
The first digit cannot be zero, so I have nine choices for it: 1, 2, ..., 9.
The remaining eight digits can be any of the ten digits: 0, 1, ..., 9.
So, for each choice of the first digit, I have 10^8 choices for the rest of the zip code.
Therefore, the total number of possible 9-digit zip codes is 9 * 10^8.