Question

In a certain country telephone numbers have 9 digits. the first two digits are the area code and are the same within a given area. the last 7 digits are the local number and cannot begin with a zero. how many different telephone numbers are possible within a given area code in this country?

Answer 1

Using the counting principle, the total number of possible telephone numbers is given by N = 1 * 1 * 9 * 10 * 10 * 10 * 10 * 10 * 10 = 9,000,000