If repetition of digits is allowed, then 56 can.
If repetition of digits is not allowed, then only 18 can.
There are 12 such numbers.
999-111=888 888 3 digit numbers can be made with numbers between 1 - 9
a lot
24 of them.
90000
2
There are 16 4-digit numbers that can be made up from 9 and 6.
210
You can select 12 numbers for the first digit, 11 numbers for the second digit, and 10 numbers for the third digit; so 12*11*10 = 1320 sets of 3 numbers can be made out of 12 different numbers.
120
1,956 different numbers can be made from 6 digits. You can calculate this by using the permutation function in a summation function, like this: Σ6k=1 6Pk = 6P1+6P2+...+6P5+6P6 What this does is calculate how many 1 digit numbers you can make from 6 digits, then how many 2 digit numbers can be made from 6 digits and adds the amounts together, then calculates how many 3 digit numbers can be made and adds that on as well etc.
150 give or take a few