Question

Today there are a total of six toll-free area codes: 800, 844, 855, 866, 877, and 888. Assume that all seven digits for the rest of a number are
possible, and determine how many toll-free numbers there are now.

Answer 1

Answer:

$6 \times 10^{7}$

Step-by-step explanation:

Total number of toll-free area codes = 6

A complete number will be of the form:

800-abc-defg

Where abcdefg can be any 7 numbers from 0 to 9. This holds true for all the 6 area codes.

Finding the possible toll free numbers for one area code and multiplying that by 6 will give use the total number of toll free numbers for all 6 area codes.

Considering: 800-abc-defg

The first number "a" can take any digit from 0 to 9. So there are 10 possibilities for this place. Similarly, the second number can take any digit from 0 to 9, so there are 10 possibilities for this place as well and same goes for all the 7 numbers.

Since, there are 10 possibilities for each of the 7 places, according to the fundamental principle of counting, the total possible toll free numbers for one area code would be:

Possible toll free numbers for 1 area code = 10 x 10 x 10 x 10 x 10 x 10 x 10 = $10^{7}$

Since, there are 6 toll-free are codes in total, the total number of toll-free numbers for all 6 area codes = $6 \times 10^{7}$