Question

How many phone numbers are possible in the (770) area code if:

For the form ABC-XXXX, A is restricted to numbers 2-9. B, C, and X can be digit 0-9. Also, the number 867-5309 is not used.

a. 6,999,999
b. 7,000,000
c. 7,999,999
d. 8,000,000

Answer 1

C

Explanation:

A can be from 2- 9 ( 8 digits)

B can be 0 to 9 (10 digits)

C can be 0 to 9 (10 digits)

Each of the X's can be 0 to 9 (10 digits)

To get the number of possibilities, we multiply them to get:

8 * 10 * 10 * 10 * 10 * 10 * 10 = 8,000,000

But now, 1 number (867-5309) is restricted, so the number of possibilities decrease by 1:

8,000,000 - 1= 7, 999, 999

Correct answer is C