how many four digit numbers can be made from the nine individual numbers?

Answer 1

Do you mean just the numbers 1-9? Or do you mean all the digits, including 0, which would be 10 digits?

If you mean 10 digits 0-9 and assuming that numbers such as 0000 are valid, then you have 10^4 = 10,000 possibilities (0000, 0001, 0002, ...., 9997, 9998, 9999 -- count 'em up, there are 10,0000).

If you really mean just nine digits, then you have 9^4 = 6,561 possibilities (you have 9 choices for your 1st digit, nine choices for your 2nd digit, 9 choices for your 3rd digit, and 9 choices for your 4th digit = 9*9*9*9 = 6,561).

You didn't say that once you use a digit it cannot be repeated. If you meant this, then the folks who are saying the answer is 9*8*7*6 = 3,024 are correct.

~ ♥ ~

Answer 2

With or without repetition? And there are actually 10 not 9 because 0 is included.

If there's repetition allowed (2222 for example), it's 9^4 for 9. If you're using 10, it's 10^4.

If there isn't any repetition(each number can be used only once per 4 digit number), then it's 9*8*7*6 (if you're assuming 9 individual numbers) or 10*9*8*7 if you're assuming the correct 10 'individual numbers'.

Answer 3

it is a permutation without repetition
with n = 9 k =4
P (n k) = n! / (n-k)! = 3024

Answer 4

9x8x7x6 = 3024

Cheers

Answer 5

8999