Two questions - one basic, one specific

[jay_shark]

The 4x rule is when you get to see 2 cards; the turn and the river .

The 2x rule is when you get to see 1 card ; either going from flop to turn , or from turn to river .

If you have Ah-Kh and the flop is 2h 3h 7c and your opponent has 7c-As . In this case you have about 12 outs .

According to pokerstove , the probability Ah-kh wins if he always gets to see both cards is ~ 46% . The 4x rule says the probability should be about 12*4=48% . It's still fairly close . It does start to break down , the higher we go but that's ok because we start to become the favorite anyway .

If you have 15 outs , then the probability you hit on the turn or river is 15/47 + 15/47 - 15c2/47c2 ~ 54.1165%

The 4x rule says it should be 4*15 =60% .

If you have 20 outs , then the probability you hit on the turn or river is 20/47 + 20/47 -20c2/47c2 ~ 67.53%

The 4x rule says it should be 20*4 =80% which is way off .