Assuming you could literally put any number into any spot (meaning you can start with zero or do 911-XXXX), then you have 10 options for each of 7 spaces, so it's 10^7=10,000,000 (ten million) possibilities.
But numbers can't start any way they choose in real life. You can't do zero first, since that's reserved to call the operator. So we have nine options first, then 6 of 10, so it's 9*10^6 = 9 million.
Now scratch out 411-xxxx and 911-xxxx since hitting those first three digits brings up information or emergency response, respectively. So we've taken out 10^4 (10,000) twice, leaving (9*10^6) - (2*10^4) = 8,980,000.
Oh, and don't forget 555-xxxx, which is an intentionally dead prefix that can be used in movies, TV, books, etc. so that they aren't giving a person's real number. Except that's not entirely true...555-1212 connects to a directory assistant in the US, and 1-800-555-1111 connects to Bell Canada. In fact, only 555-0100 through 555-0199 are reserved for fictitious use now; any others may be put to use someday. So that's 100 more numbers we can remove, bringin us down to
(9*10^6) - (2*10^4) - 100 = 8,979,900 genuinely possible 7-digit phone numbers
out of
10,000,000 theoretically possible 7-digit phone numbers.
10000. 0000 to 9999
I think you r cheating Mr.Cheater
There are several possiblites, here are some: 7123456 6987543 7102394 please add some more below, viewers!
All numbers 9,001 through 9,999.
There are 90 two digit numbers, 10 through 99. There are 18 two digit numbers containing a 9. They are 19, 29, 39, 49, 59, 69, 79, 89, and 90 through 99. Therefore, there are 72 two digit numbers that do not contain a 9.
There are 17 such numbers.
3 digit numbers are lessthan 4 digit numbers
A 3 or 4 digit number.
89999 5-digit numbers are there in all... That is the numbers from 10000 to 99999... Wrong. There are 90000 five digit numbers in all. When you start to count you count from 10001 to 99999which is 89999 numbers. To that you add the one number 10000. 89999+1=90000
3897
The ratio of the number of one-digit prime numbers to the number of one-digit composite numbers is one to one. The one-digit prime numbers are 2, 3, 5, and 7. The one-digit composite numbers are 4, 6, 8, and 9. Therefor, the ratio is 4:4, which simplifies to 1:1.
There are four of each.