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Old 12-12-2005, 03:10 PM
Megenoita Megenoita is offline
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Default Need help with some flop probability calcs

Hi guys,

Trying to do some work here...

how do I calculate how often JT flops a straight? I have the answer; I'm wondering HOW.

Thanks,
M
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  #2  
Old 12-12-2005, 03:17 PM
pzhon pzhon is offline
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Default Re: Need help with some flop probability calcs

There are 50 choose 3 = 50*49*48/(3*2*1) = 19600 flops. You can flop a straight that is ace-high, king-high, queen-high, or jack-high. For each possible straight, there are 4 choices for the suit of each card, except that you should subtract off the straight flush. So, the total number of flopped straights is 4*(4*4*4-1) = 252. The probability of flopping a straight is 252/19600.
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Old 12-12-2005, 03:39 PM
Megenoita Megenoita is offline
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Default Re: Need help with some flop probability calcs

Thanks...I'm going to work on this...
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Old 12-12-2005, 03:45 PM
Megenoita Megenoita is offline
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Default Re: Need help with some flop probability calcs

Okay, so I did this calculation correctly except I divided by 117600 total flops. Why exactly do we divide by 6? It's b/c of the permutations (?), right? The number of ways the same flop can come on the board?

Also, the sheet I was given said that a connector like JT flops a straight .31% of the time, not over 1% which you said. Is that sheet just wrong?

Thanks,
M
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Old 12-12-2005, 04:48 PM
pzhon pzhon is offline
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Default Re: Need help with some flop probability calcs

[ QUOTE ]
Okay, so I did this calculation correctly except I divided by 117600 total flops. Why exactly do we divide by 6? It's b/c of the permutations (?), right? The number of ways the same flop can come on the board?

[/ QUOTE ]
Yes. It's important to be consistent. If you distinguish between A[img]/images/graemlins/spade.gif[/img] K[img]/images/graemlins/spade.gif[/img] Q[img]/images/graemlins/spade.gif[/img] and K[img]/images/graemlins/spade.gif[/img] Q[img]/images/graemlins/spade.gif[/img] A[img]/images/graemlins/spade.gif[/img], then you have 6 times as many flops, and 6 times as many straights as I calculated. The ratio will be the same.

[ QUOTE ]

Also, the sheet I was given said that a connector like JT flops a straight .31% of the time, not over 1% which you said. Is that sheet just wrong?


[/ QUOTE ]
That sheet is wrong. In this table, Mike Caro confirms that the probability of getting a particular straight is about 0.33%, and that QJo flops a straight 0.98% of the time. QJo only has 3 possible flopped straights as opposed to 4 for JT.

Perhaps you are looking at data that was caclulated for AKs, though that should be 0.32%.
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  #6  
Old 12-12-2005, 09:29 PM
Megenoita Megenoita is offline
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Default Re: Need help with some flop probability calcs

If you don't mind, P, then how do we do the problem of KQ flopping a pair? I know it's about 16% each or 32% total.

The way I was doing it was apparently wrong but I somehow came to the right answer...how do you do this?

Thanks,
M
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  #7  
Old 12-13-2005, 12:27 AM
Megenoita Megenoita is offline
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Default Re: Need help with some flop probability calcs

bump-anyone?
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  #8  
Old 12-13-2005, 02:49 AM
Megenoita Megenoita is offline
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Default Re: Need help with some flop probability calcs

For anyone who might care, one way to find how often the flop will contain 1 pair for you if you have KQ, for instance, is this:

How many flops will NOT contain a K or Q:

44/50 x 43/49 x 42/48 = .6757 - 1 = .3243
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  #9  
Old 12-13-2005, 03:09 AM
ohnonotthat ohnonotthat is offline
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Default Re: Need help with some flop probability calcs

That is the correct way to calculate whether you will flop one pair OR BETTER.

It accounts for ALL improvements other than a flopped straight.

Note that this does not tell you the % of time you'll flop TOP pair; some of these flops will contain [one or more] Aces.
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  #10  
Old 12-13-2005, 04:25 AM
Megenoita Megenoita is offline
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Default Re: Need help with some flop probability calcs

Yes, you are right; it doesn't tell us how often we flop top pair. I can calculate how often we flop top pair OR BETTER, though.

Flops that will have at least a K or Q and NO ace:

6/50 x 45/49 x 44/48 + 40/50 x 39/49 x 6/48 + 40/50 x 6/49 x 44/48 = 27%.

So, when holding KQ, we know we'll flop top pair or better slightly better than 1 in 4 times. That means 83% of the time we flop a pair, it will be top pair (or better).

M
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