# Homework Help: Help me

1. Dec 5, 2007

### rani1788

Hi, i have a test tommorow and I can't seem to figure out these two problems:

1. Atm codes: to use an automated teller machine, you generaaly must enter a four-digit code, using 0-9. How many four digits codes are possible if repetition of digits is permitted?

2. Licence plate: a license plate is to have uppercase letters or digits. Determine the number of license plates possible if repetition is permitted and if any position can contain either a letter or digit with the expection that the first position caanot the letter o or the number 0.

Can some one help me?

2. Dec 5, 2007

### Staff: Mentor

Thread moved to Homework Help. Welcome to the PF, rani. How would you approach the first problem? Think of it as a pure counting exercise. If you count from 0 to the maximum number allowed by 4 digits, how many counts are there?

And then how can you extend that to other bases? (Like base 26 for letters, versus base 10 for counting numbers)