Question

Phone numbers consist of a three-digit area code followed by seven digits. If the area code must have a 0 or1 for the second digit, and neither the area code nor the seven-digit number can start with 0 or 1, how many different phone numbers are possible?

Answer 1

1.28 * 10^10

Explanation:

Area Code: 8 * 2 * 10

7 digit number: 8 * 10 * 10 * 10 * 10 * 10 * 10

The total number of area codes is 160

8,000,000 * Area Codes

1.28*10^10