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# How many phone number combinations are there in the U.S? Random Question! Ha.?

So I just randomly pondered this question, and I tried desperatly to figure out out, but I couldn't. So how many possible phone number combos are there?!

I thought of it like.. 10 different possible numbers..including zero.

11 slots for the number including 1. 1 ### ### ####

Now..you figure it out! lol, i'm just curious! :D

### 11 Answers

- 1 decade agoFavorite Answer
You are on the right track

There are actually only 10 digits in a US phone number. 1 is the country code and they all share that.

you just multiply

10x10x10 x 10x10x10 x 10x10x10x10

You could also write that as 10^10

This equals 10,000,000,000

Which is 10 Billion

The answer above me is clearly wrong. Yes there are some excluded area codes, but there are more than 10 million people in just some of the states. Often some people have more than 1 number, I had 3 at one point.

There about 300 million people in the US, so there are way more phone numbers than 300 million.

- tech_guy_towtLv 56 years ago
But, don't we need to take into account that the first position of both the area code and the phone number can't start with 1 or 0? You can't have 055 023-3234. So this might be better reflected as

(8x10x10)x(8x10x10)x(10x10x10x10) the brackets are just to separate the numbers

Of course you have to exclude 555 and other such area codes, so I'm not sure how to reflect this mathematically.

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- 1 decade ago
Well, as you said, we have 10 numbers per slot. Except I believe no numbers have area codes beginning with 1, and no local numbers begin with one (since 1 dials out to begin typing in an area code)

Then we have 9 spots of 10 numbers, and 2 spots of 9 numbers:

so then the answer is 10^9 * 9^2 = 81E9 (or 81,000,000,000 possible phone numbers)

- 1 decade ago
Well the first one wont be included so just 10 possible numbers including the zero is what we would have to use. Although the number would be less because i dont believe area codes would start with a 0...or even worst 000....or just have a number of just all same numbers....but if it was possible then your answer would be 10 to the tenth power, or 10^10.....which is 10 times 10...ten times.....youll end up with 10,000,000,000 or ten billion different combinations.

- 1 decade ago
Assuming there is a 1 in front of every number, there are 10 slots each with 10 possible digits. That is 10 billion possible numbers (10 to the power of 10).

- Anonymous6 years ago
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