How many seven-digit telephone numbers are possible if the first two digits cannot be twos or zeros?

Question

How many seven-digit telephone numbers are possible if the first two digits cannot be twos or zeros? ​

Quizplus · Accepted Answer

For the first digit, there are 8 choices (1, 3-9), and for the second digit, there are also 8 choices (1, 3-9), because the digits cannot be 2 or 0. For the remaining five digits, each can be any number from 0 to 9, giving 10 choices each. Therefore, the total number of possible telephone numbers is 8 (choices for the first digit) * 8 (choices for the second digit) * 10^5 (choices for the remaining five digits) = 6,400,000.

How Many Seven-Digit Telephone Numbers Are Possible If the First