Brian S. answered • 04/26/19

Math Instructor, B.A. Mathematics

Since it has been established that there is only 3 number prefixes we just focus on the the 4 digit suffixes. if we start the suffixes at 0000 and end with 9999 there are 10,000 different suffixes to choose. Multiply that with the 3 prefixes the answer is 3 * 10,000 = 30,000 different phone numbers