Question

For years, telephone area codes in the United States and Canada consisted of a sequence of three digits. The first digit was an integer between 2 and 9, the second digit was either 0 or 1, and the third digit was any integer from 1 to 9. How many area codes starting with a 4 were possible?

Answer 1

The first number had to be 4, so only one option for the first number.

The second number was either 0 or 1, so two options for the second number.

The third number was between 1 and 9, so nine options for the third number.

Multiply each number of options together for total options:

1 x 2 x 9 = 18 different codes could start with 4.

Answer 2

It's given that the first number has to be 4, so there's one option for the first.

The second number can be 0 or 1, resulting in 2 options.

The third number is an integer between 1 and 9, so there are 9 options for the third number.

Multiply each number of options together for total options:

1 x 2 x 9 = 18 different codes