A phone number is composed of 10 digits. The first three are the area code the other 7 are the local telephone number which cannot begin with a 0. How many different telephone numbers are possible in a single area code?
[Math] How many different phone numbers are possible within an area code
combinatorics
Best Answer
From Wikipedia http://en.wikipedia.org/wiki/North_American_Numbering_Plan:
Each three-digit area code may contain up to 7,919,900 unique phone numbers: