How many numbers can you make with 4 digits used only once?

Answer 1

Well, darling, if you're using 4 digits and each one can only be used once, you can make a total of 9,720 different numbers. That's because you have 10 choices for the first digit, 9 choices for the second digit, 8 choices for the third digit, and 7 choices for the fourth digit. Multiply all those together and voilà, you've got yourself a whole lot of numbers to play with.

Answer 2

Because of the question's ambiguity, it is hard to tell exactly what is meant. However, to cover all possibilities:

If there are four numbers and each is used once, there are 4! = 4 x 3 x 2 x 1 = 24 different combinations.

If there are the 10 digits used to make a four-digit number, using each once, we have 10!/(10-4)! = 10!/6! = 10 x 9 x 8 x 7 = 5040 different combinations.

Or does he mean this?

Using the binary numbering system.
Binary Decimal
0000 0
0001 1
0010 2
0011 3
0100 4
0101 5
0110 6
0111 7
1000 8
1001 9
1010 10
1011 11
1100 12
1101 13
1110 14
1111 15

Answer 3

Oh, what a happy little question! You can make 9,720 different numbers with 4 digits, each used only once. Isn't that just wonderful? Just think of all the beautiful combinations you can create!

Answer 4

750