Question

This problem is a bit vague and I need help.
http://imgur.com/hBidGqI
I did the first bit, and i'm working on the rest now. I just need to be sure.

Answer 1

Theoretically means to ignore any weird restrictions that might be applied to phone numbers. Like for example, in the real world, at least in the United States, you can't have a phone number beginning with 911 or 555.

But we ignore all of that for this problem.
So let's take some random area code, maybe 817.

How many possibilities for the 7 digits that follow?

Well... 10 possible numbers can go in the first slot,
Numbers can certainly repeat in a phone number,
so we have 10 possible numbers available to the second slot.

Do you see a pattern here? :)

Answer 2

so 10^7?

Answer 3

yes 10^7 is correct @cbreadbox

Answer 4

If I'm understanding this correctly,
it seems like for part c,
they just want you to multiply your result from b by 301.

301 area codes were being used,
so you have 301x10^7 possible phone numbers (including area codes).

Answer 5

That makes sense now. I understand the rest of the problems.