Quote:
Originally Posted by IceKing
For example if we count how many four of kind hands with out jokers, I think that is 13*COMBIN(20;4)=62985
13*12*C(24,4)*24 = 39,783,744
13*12 possibilities for the ranks (counting order so as to distinguish between which is the quads and which is the extra card).
C(24,4) ways to pick 4 from a given rank, and 24 ways to pick from the other rank.
With jokers that becomes:
C(13,2) * 24 * { [C(34,4) - C(10,4)] + [C(34,4) - C(10,4) - 24*C(10,3)] }
= C(13,2) * 24 * {2*[C(34,4) - C(10,4)] - 24*C(10,3)} = 167,454,144
C(34,4) ways to draw 4 from either the quads rank or the jokers. But we don't want 4 jokers because that would be 5 of a kind, so we subtract C(10,4) which is the #ways to pick 4 jokers.
But notice that if there are 3 jokers, then only the higher rank can be the quads. That's why I have C(13,2) instead of 13*12 (think about this until it makes sense). In my unsimplified line, the first set of [ ] includes the case of 3 jokers. The second one does not, ie it subtracts the #ways to get 3 jokers which is 24*C(10,3). So we have C(13,2)*6*[quads including 3 jokers] + C(13,2)*24*[quads w/o 3 jokers]. Just as there are C(13,2) ways to choose 2 ranks and let the higher rank be quads, there are C(13,2) ways for the lower rank to be the quads, so that's the 2nd thing being added (but it requires there to be fewer than 3 jokers, otherwise the higher rank would be the quads).
Finally, I just factored out the C(13,2)*24 and added the brackets together which results in my 2nd line.
As for the other hands, I'll get to them another time or someone else can take a stab.
EDIT #2 -- oh you said 4-card hands. Ok I'll leave this up now that I wrote it all. In a separate post I'll answer your actual question.
Last edited by heehaww; 08-23-2015 at 01:37 PM.
Reason: Edit #1: 24 of a rank, not 6.