Quote:
Originally Posted by Tom1975
First, we need to count the total number of possible flops. We know the identity of 6 cards, so that leaves us 46 cards left choose from. Therefore there are C(46,3)=(46*45*44)/(3*2*1)=15180 possible flops.
Now we need to count the number of those flops which will contain 3 flush cards. There are 7 flush cards left, therefore there are C(7,3)=(7*6*5)/(3*2*1)=35 flops.
So the final answer is 35/15180=.0023
If hero has suited cards and we assume random suit distribution for villains then we have hero hitting a flush on the flop C(11,3) = 165.
So, you and two villains all have the same suit of cards, the chance that you flop a flush is about 1/5 the chance of you getting the desired monochrome flop when villains have random suit distribution.
alternatively, you can count it by considering all the possible villain holdings (i.e. 100% range) vs their flush holdings. You can see 5 cards so villan's combined hole cards are C(47,4) = 47*46*45*44 / 4 * 3 * 2 = 178365
and the combinations where they hold the same suit as the board are C(8,4)=70. So, when you see that your suited cards have flopped a flush (about 1% of the time), two villains who came along with 100% PF ranges will also have a flush 70/178,365 = 0.039% of the time (3.9e-4). This is more of a first person perspective (i.e. how likely is it that they both have the same suit given that I just hit my flush).
Of course villains generally don't play a 100% preflop range. When we get to the weakest part of a players range, most prefer suited over unsuited. E.g. villain might have 45s in his range but not 45o.