If repetition is allowed . . . . . 343
If repetition is not allowed . . . . . 210
100,000
12
24
There are 504 such numbers.
823543
840
9999
100,000
12
512
24
There are 504 such numbers.
There are 60480 numbers.
823543
6
There are 5! = 120 such numbers.
There are 7,290 different 4-digit numbers that can be formed from the digits 1-9 without repetition.