Question

How many phone numbers (without area codes) are possible? The first digit cannot be 0 or 1.

Answer 1

Explanation:

For the first digit, there are 8 numbers to choose from (2, 3, ..., 9).

For each remaining digits, there are 10 numbers to choose from (0, 1, ..., 9).

Choose 6 of them. Repetition is allowed, and order matters.

There are 10⁶ possible choices.

There are 8×10⁶ possible phone numbers.