Telephone area codes are three-digit numbers of the form XXX.

Question

a) Originally, the first and third digits were neither 0 or 1 and the second digit was always a 0 or 1. How many three-digit numbers of this type are possible?

b) Over time, the restrictions listed in part a) have been altered, currently, the only requirement is that the first digit is neither 0 or 1. How many three-digit numbers of this type are possible?

c) Why were the original restrictions listed in part a) altered?

Answer 1

(a) 8 * 2 * 10 = 160

(b) 8*10*10 = 800