Question

Assuming that there are 10 digits used as telephone number and the area code is a fixed 3 digit number. How many different telephone numbers could be created?

Answer 1

9,999,999,999,987 Of course, if 'numbers' with leading digits e.g. 0 000 087 654 321, and all zeros, are not counted as valid 'numbers' then there are 13 less possibilities. i.e. There are only 9,999,999,999,987 possibilities.