NOTE: I posted this a while back, and I still think the exercise has validity. If you can't do this, then you need to learn how to do it. Before trying to figure out the answer, take an "off the top of your head" guess, just to see how close you are. When I was playing LHE seriously, I would make a note of any decisions that I thought might be close, and then do the math afterwards to see if my decision was correct, incorrect, or close one way or another. I think that's a VERY important part of playing poker professionally or semi-professionally.
If you remember doing this, please let people who have never seen it before give it a shot. If you are very good and surely know the answer, PM it to me.
On the turn, there are 5.5BB in the pot, after rake. You're thinking about whether to semibluff again, or take a free card.
You have a huge draw, with 18 live outs. (For the sake of clarity, there are 46 unseen cards.) How often does your semibluff have to be successful (ie, lead to a fold from an opponent) to be a totally breakeven play? The betting ends after the turn, so don't concern yourself with implied odds. You will never be raised. Your opponent will either call or fold. You are always drawing to exactly 18 outs, and you are never ahead.
Please show all work, and goodluck.
This should be good for some of the people less experienced with the math involved in LHE.
Wang
PS- I haven't really seen an in depth discussion of this concept here, or in Theory of Poker or anything, but I may have missed it. I haven't read much (books or here) in a long time. I sit down at my computer or in front of the TV with a pen and piece of paper and do stuff like this all the time.

