How many ten-digit phone numbers are possible in the North American Numbering Plan?

Express your answer in scientific notation.How many ten-digit phone numbers are possible in the North American Numbering Plan?
3628800





3.6288 x 10^6





Taking the fact that you can get number 0000000001 to 9999999999How many ten-digit phone numbers are possible in the North American Numbering Plan?
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Here are a few things to remember about NANP:


Area codes may not start with 0 or 1. Nor may they contain a 9 as the middle of the 3 digits.


Exchange Numbers (the first 3 digits, but not the area code) may not start with a 0 or 1.





Therefore, the whole series of number may be as follows


[2-9][0-8][0-9] [2-9][0-9][0-9] [0-9][0-9][0-9][0-9]








Ok, I was never great at math, so I had to think about this a bit more.


Your answer is combinations of area code multiplied by combinations of exchange (or central office code) mutiplied by combinations of Station code.





So, area code = [8 x 9 x 10] = 720


Exchange code = [8 x 10 x 10] = 800


Station Code = [10 x 10 x 10 x 10] = 10,000





Product of all that is 5,760,000,000.


Expressed in scientific notation, the result is 5.76 x 10^9