Question

If every seven digit whole neumber is a possible phone number, except those that begin with 0 or 1, what fraction of telephone numbers begin with 9 and end with 0?

Answer 1

wouldn't it be 1/8 * 1/10 ?

Answer 2

Since the first number cannot be 0 or 1, you have 1/8 probability of getting a 9. The probability of the last number being 0 is 1/10.

The probability of two or more events all occurring is found by multiplying the individual probabilities.

I hope this helps you to understand the process to solve similar problems. Thanks for asking.