162
-- If the same digit may be repeated, then 64 can be made. -- If the same digit may not be repeated, then 24 can be made.
4*3*2*1 = 24
-- If 'zero' is always the first digit, then we're pretty darn sure that no other digit can be repeated in the same 2-digit number, since there's only one digit left to be filled in. -- If 'zero' is always the first digit, then there are exactly six possible 2-digit numbers: 00 01 02 03 04 and 05.
9
162
With repeated digits, 43 = 64 Without repeated digits, 4*3*2 = 24
-- If the same digit may be repeated, then 64 can be made. -- If the same digit may not be repeated, then 24 can be made.
4*3*2*1 = 24
-- If 'zero' is always the first digit, then we're pretty darn sure that no other digit can be repeated in the same 2-digit number, since there's only one digit left to be filled in. -- If 'zero' is always the first digit, then there are exactly six possible 2-digit numbers: 00 01 02 03 04 and 05.
9
There are 3 values (1, 2, 3) for each of the 4 digits. Therefore, there are 3*3*3*3 or 81 four digit numbers that can be formed.
36
If the digits can be repeated, then there are (5 x 5 x 5 x 5) = 625 different four-digit numbers.If the digits can't be repeated, then there are (5 x 4 x 3 x 2) = 120 different four-digit numbers.
Six possibilities: 34, 35, 43, 45, 53, 54.
6*5*4*3*2*1=720 possible numbers
If the digits are repeatable, the answer is 4*4*4*4. If the numbers cannot be repeated, then it is 4*3*2*1.