3 * (2 - 1)
9
012258
6 for 3-digits, 6 for 2-digits, 3 for 1-digits, and 15 for all of the combinations
111, 121, 222, 212
3*3*2*1 = 18 of them.
6
The highest number you can make out of the digits 2 4 0 and 1 is 4210.
123,456 would be the smallest number using all 6 digits. You arrange the numbers from lowest to highest.
111, 121, 222, 212
Six, if you don't repeat any digits.
write the largest number you can make using each of the digits 7,1,0,2, and 9 just once
If you use them only once each, you can make 15 combinations. 1 with all four digits, 4 with 3 digits, 6 with 2 digits, and 4 with 1 digit. There is also a combination containing no digits making 16 = 24 combinations from 4 elements.