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View Full Version : Probability for flopping OESD/straight with connectors

FlyingStart
09-02-2005, 08:36 AM
If you see a flop with 45-9T, what is the probability that you flop an OESD or a straight?

09-02-2005, 09:25 AM
flopping a straight 1.3%
flopping an 8 out straight draw 10.5%

I think

LetYouDown
09-02-2005, 09:33 AM
For an OESD (not double gutshot), I come up with:

3 * (16 * 40)/C(50,3) = ~9.8%

09-02-2005, 10:03 AM
Someone check my math here . . . I believe the odds against flopping a str8 or OESD are 7.5 to 1 against. The probability of this event is 1/8.5 or approx 12%.

The math. Lets take 45 as an example
for an OESD you need either a 2,3 3,6 or 6,7 on the flop.
there are 16 combinations of each of these two card combos for a total of 48 combinations. Each of these 48 combinations can combine with the 48 unseen cards left in the deck to give you 2304 flops which give you an OESD or a str8 (some of the 48 remaining cards complete your str8). There are 19,600 flops possible. Therefore the odds against flopping a str8 or OESD are (19600 - 2304)/2304 = 7.5 to 1.

A more intresting number to consider when looking at hands like 45 preflop would be to calculate the # of flops which give you a str8, OESD, two pair, trips, boat, or quads. I think the odds for this are between 5 to 1 and 6 to 1 against.

LetYouDown
09-02-2005, 10:23 AM
The problem with your math is it includes the odds of actually flopping the straight itself...not just the draw. Hence the 40 in my calculation vs. your 48.

09-02-2005, 10:28 AM
I thought that is what the poster asked for. The odds for flopping either the str8 or the OESD

FlyingStart
09-02-2005, 10:33 AM
Thx.. so with a SC you should have about 4-1 on flopping a good draw?

LetYouDown
09-02-2005, 10:37 AM
Define good draw. Didn't realize suited had entered the equation.

09-02-2005, 11:03 AM
I'd be real cautious about counting flush and flush draws into the equation because you can hit your flush and lose to a higher flush, esp. with 45s.

FlyingStart
09-02-2005, 11:17 AM
The original post was just for the straights.

Higher flush is a possibility yes, but I just want some general idea of how often you flop a straight or flush draw with SC. Even though you sometimes run into higher flushes I would still count a low flushdraw as a good draw

LetYouDown
09-02-2005, 11:19 AM
Well, it's just a draw. A good draw is a nut draw or an OESFD. But that's semantics anyway.

punter11235
09-02-2005, 05:34 PM
Try this (http://forumserver.twoplustwo.com/showthreaded.php?Cat=&amp;Number=2948434&amp;page=0&amp;view=c ollapsed&amp;sb=5&amp;o=14&amp;vc=1) one for complete answer for this and similair questions.