Phone Number Numbers ```Name: Jay Status: student Age: N/A Location: N/A Country: N/A Date: N/A ``` Question: I recently read in this health magazine that it can be 823,542 phone numbers without the same number. According to my me if I miscalculated? Unless the there are numbers they won't use. Replies: Jay, I assume you mean a phone number, without the area code. You are correct that there are numbers that won't be used , for example 0000000 would probably ring the operator. This deletes from availability any of the digits beginning with 0, such as 0000000, 0000001, 0000002, 0000003.......0999999, or 1, 000, 000 combinations. You could add to this any other 'special' numbers, such as "911" where any number beginning with 911 would not work because 911 would be contacted after the first 3 digits were dialed. Therefore 9110000, 9110001, 9110002 ...9119999 could nto be used. (This problem excludes 10,000 numbers.) There might be other unusable combinations in your community which would then remove from use those combinations. Try to identify for your community which number combinations are not useable, and then subtract the combinations from the total possible. If all combinations could be used the acceptable numbers would be 0000000 to 9999999. This gives 10 million combinations. Just citing the problems I mentioned above, we have available 10,000,000 less 1,000,000 or 9 million combinations. We must also subtract 10,00 unsuitsble combinations beginning with 911. Try this exercise for you community after checking which digits are not used or are dedicated to special use. Thanks for using NEWTON! Ric Rupnik Click here to return to the Mathematics Archives

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