That depends upon whether you are allowed to repeat numbers. If you are allowed to repeat, that means that all seven digits (say 1 through 7) can be used in each of the four positions of your...
I think you'll be surprised how many there are, and will understand why they are not being listed!Any 6 from 20: (20 x 19 x 18 x 17 x 16 x 15)/(6 x 5 x 4 x 3 x 2)= 38,760If you allow the same numbers...
This questions can be rewritten as 52 choose 6 or 52C6. This is the same as (52!)/(6!(52-6)!) (52!)(6!46!) (52*51*50*49*48*47)/(6*5*4*3*2*1) 14658134400/720 20358520 There are 20,358,520 combinations...