Join Date: Jun 2007
Posts: 5,951
First, this type of thinking only works on the river, because future streets can impact your true equity. This is poker and not math related, but for example say an opponent either has the nuts 50% or a bluff 50%. If he bets $0.50 into the $1 pot with his entire range, and there is only one street of betting, you can easily call because he is bluffing half the time and you only have to be right 25% to call. But if there are two streets of betting, you probably have to fold, since on the next street he can bet much bigger.
Now to the formula. If they bet p of the pot, then you have a price of (p/(1+2p) ). So you should call if x >= p/(1+2p).
For example, if they bet half the pot, p = 0.5, and you should call if x >= 1/4.