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Best line for 4 tricks?

#1 User is offline   Walddk 

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Posted 2009-April-10, 06:28

We had this interesting (simple?) suit combination on vugraph Thursday:

AK1096

87

You need four tricks. No inferences from the auction (opps did not bid), and you have plenty of entries to both hands. How would you play without using Suitplay or the like?

Most commentators got it wrong until Mark Horton and Walter Johnson made thorough calculations and told us what the odds are.

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#2 User is offline   se12sam 

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Posted 2009-April-10, 06:32

Isnt it simply cashing the top two cards in the suit?

Wins when they are 3-3, 4-2 with a doubleton honor or 5-1 with a singleton honor.
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#3 User is offline   Free 

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Posted 2009-April-10, 06:56

I think it's finessing twice, but not sure
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#4 User is offline   gnasher 

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Posted 2009-April-10, 08:45

I would have guessed that cashing AK was best, but, comparing that with taking two finesses:

Leading from the top loses to:
- 6/15 of the 4=2 breaks ~= 10%
- 4/6 of the 5=1 breaks ~= 5%
- All of the 6=0 breaks ~= 1.5%

Taking two finesses loses to:
- 4/20 of the 3-3 breaks ~= 7%
- 1/15 of the 4=2 breaks ~= 1.5%
- 2/6 of the 5=1 breaks ~= 2.5%

So two finesses is better. Or (at least as likely) I've misanalysed it again.
... that would still not be conclusive proof, before someone wants to explain that to me as well as if I was a 5 year-old. - gwnn
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#5 User is offline   dburn 

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Posted 2009-April-10, 09:24

This is one of the most often mangled suits in bridge - even Zia doesn't know how to play it. Two finesses is certainly correct: a simple check will show that this loses to QJx, QJ doubleton and a singleton honour offside, while gaining against a small doubleton, a small singleton or a void offside. The chance of each of these holdings, given roughly by gnasher above (although he should not have counted both 6-0 breaks), is:

QJx offside 7.1056%
QJ offside 1.6149%
Q or J offside 2.4224 %
Total losing cases for two finesses 11.1429%

Small doubleton offside 9.6894%
Small singleton offside 4.8447%
Void offside 0.7453%
Total losing cases for playing from top 15.2795%
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#6 User is offline   jdonn 

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Posted 2009-April-10, 10:03

What I find amazing about this is that it's not even close.
Please let me know about any questions or interest or bug reports about GIB.
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