Question
Assume that you are dialing a long distance telephone number. If you enter the dialing digits in the format I XXX YYY ZZZZ, what do the $1, \mathrm{XXX}$, YYY and ZZZZ digits represent?
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Phone numbers in North America have 10 digits: a threedigit area code, a three-digit exchange number, and the four final digits that make each phone number unique. Neither area codes nor exchange numbers can start with 0 or $1 .$ Prior to 1994 the second digit of the area code had to be a 0 or 1 Sixteen area codes are reserved for special services (such as 911 and 411 ). In $1994,$ the last area code was used up and the rules were changed to allow the digits 2 through 9 as the middle digit in area codes. How many different exchange numbers were possible prior to $1994 ?$
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Phone numbers in North America have 10 digits: a threedigit area code, a three-digit exchange number, and the four final digits that make each phone number unique. Neither area codes nor exchange numbers can start with 0 or $1 .$ Prior to 1994 the second digit of the area code had to be a 0 or 1 Sixteen area codes are reserved for special services (such as 911 and 411 ). In $1994,$ the last area code was used up and the rules were changed to allow the digits 2 through 9 as the middle digit in area codes. How many different area codes were possible prior to $1994 ?$
Phone numbers in North America have 10 digits: a threedigit area code, a three-digit exchange number, and the four final digits that make each phone number unique. Neither area codes nor exchange numbers can start with 0 or $1 .$ Prior to 1994 the second digit of the area code had to be a 0 or 1 Sixteen area codes are reserved for special services (such as 911 and 411 ). In $1994,$ the last area code was used up and the rules were changed to allow the digits 2 through 9 as the middle digit in area codes. How many different phone numbers were possible after $1994 ?$
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