2006-06-29 23:52:52 · 8 answers · asked by dnd 1 in Science & Mathematics ➔ Mathematics
If there was only one digit, there would be 10 (0-9)
Two digits, 100 (00-99)
Three digits, 1000 (000-999)
Hey, there might be a pattern here
So 10 digits, 10,000,000,000 (0000000000-9999999999)
2006-06-29 23:58:41 · answer #1 · answered by Bill S 6 · 1⤊ 0⤋
Theoretically, the answer is 10^10, or ten thousand million numbers. In practice, area codes do not begin with 0 or 1 as those have specific actions associated with them, which reduces the combinations to eight thousand million. Prefix numbers also do not begin with 0 or 1 for similar reasons, which reduces the number to six thousand, four hundred million.
This is actually an increase over past systems, where the middle digit of an area code was required to be 0 or 1, and where the middle digit of a prefix could not be 0 or 1. Those prohibitions were lifted as the need for more numbers came about. even with 6.4E09 numbers, we're starting to strain the current system and reform will probably be needed in the next decade or two.
(By the way, this applies to only the North American system. Other nations have there own system based on country codes.)
2006-06-30 00:10:28 · answer #2 · answered by Ѕємι~Мαđ ŠçїєŋŧιѕТ 6 · 0⤊ 0⤋
That's very simple.
Area code: three numbers with a possible range 000-999, or 1,000. However, not all are in use. Call this A.
Prefix: three numbers with a possible range of 000-999, or 1,000. However, not all are in use. Call this P.
Number: four numbers with a possible range of 0000-9999, or 10,000. All can be used. Call this N.
A*P*N = 1,000 * 1,000 * 10,000 or 10,000,000,000 (10 billion or 1*10^10). If you know how many area codes and prefixes are actually in use you can get the actual number.
2006-06-30 00:00:12 · answer #3 · answered by Anonymous · 0⤊ 0⤋
Yes, because there are seven slots for the seven digits.
The first slot can have each of the 10 digits
The 2nd slot can have each of the 10 digits
The 3rd slot can have each of the 10 digits
The 4th slot can have each of the 10 digits
The 5th slot can have each of the 10 digits
The 6th slot can have each of the 10 digits
The 7th slot can have each of the 10 digits
Multiply them all to get the possible phone numbers using 10 digits in 7 slots
10^7 = 10,000,000 phone numbers
^_^
2006-06-30 00:37:36 · answer #4 · answered by kevin! 5 · 0⤊ 0⤋
Because of prefixes and area codes. I could have the same number as you, almost. Your number could be 111-111-1111, while mine could be exactly the same excepting one variant. You can see Dr. Math's response. The link is below.
2006-06-30 04:34:28 · answer #5 · answered by The Nana of Nana's 7 · 0⤊ 0⤋
well, if there were only 3 numbers we would get 999 combinations. the more numbers we add to this equation, we get exponentially more numbers to use.
2006-06-29 23:56:49 · answer #6 · answered by dallaschrist 1 · 0⤊ 0⤋
because the tenth number is 0 and it can be used in several different combinations.
2006-06-30 03:20:15 · answer #7 · answered by lewis o 1 · 0⤊ 0⤋
just because there are millions of possible combos using 10 digits
2006-06-29 23:55:47 · answer #8 · answered by davemo 3 · 0⤊ 0⤋