Question

how many 7-digit phone numbers can be formed if the first digit cannot be 0 or 1, and any digit can be repeated​

Answer 1

8 × 10⁶

Explanation:

The first digit can be any number from 2 to 9. We can select any of the eight digits.

We can select the remaining digits in ten different ways.

Each choice is independent, so we can multiply the choices together.

N = 8 × 10 × 10 × 10 × 10 × 10 × 10

= 8 × 10⁶ possibilities

There are 8 × 10⁶ possible seven-digit phone numbers.