Author Topic: Poco's Play Problems  (Read 533 times)

poco1

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Poco's Play Problems
« on: October 21, 2019, 08:21:21 PM »
Hi everybody!

I started "Poco's Play Problems" last Friday and will be doing the next one on Friday 1st November. I am attaching the hands from that session, along with a brief commentary regarding the point of the hand. Please remember that the bidding is, more or less, what would be expected in the UK. Those of you in the United States may well find it different to your own bidding methods. That doesn't matter... the problems are PLAY problems.... I hope that you enjoy them.

Curls77

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Re: Poco's Play Problems
« Reply #1 on: October 21, 2019, 08:24:45 PM »
TY so much Colin :)
I am sure IACers will enjoy this thread, and hope they study and discuss hands u post in here. Join poco's problems, every 2nd friday at 1800 utc, 7pm uk, 2pm NY  (times will change with next clock move, but it will be updated, watch iac diary).

kenberg

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Re: Poco's Play Problems
« Reply #2 on: October 21, 2019, 10:30:16 PM »
These are very nice hands.

I think there is a subtle point  in number 8 I am far from sure how to resolve it.  The early  play is heart to the K, another heart, taken by the A. A club from the board, S plays the T or the J,  holding the trick, and S plays back a diamond. Assume declarer takes it, although he might duck.  Duck or not, declarer later gets the lead and leads his remaining club. N follows with the 9. Now what? If S started with K third. it's hopeless. And not great if N started with K fourth although declarer at least gets 2 tricks if he finesses. So assume N still has exactly one more club. Which one? If he still has the J or the T to go with his 93 then playing the A drops the now stiff K in the S hand. If N has the K to go with the 93 then playing the Q is right.

Let's say that on the first club S played the J. At decision time N has played the 9 and 3. Did S start with KJ  tight (we must play the A) or with JT tight (we must play the  Q)?

There is something of a restricted choice aspect to this, especially if we credit S with the courage to pay the T from KT tight. The T would not be crazy from KT since the K would surely surrender the suit. But it's a tough play.

I like the hands a lot, including, or maybe especially, this last one.
Ken

wackojack

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Re: Poco's Play Problems
« Reply #3 on: October 22, 2019, 10:10:52 AM »
Interesting observation Ken. 

Let us say that South is a good player and would always smoothly play J from KJ and 10 from K10.  Also South would play low from Jx or Kx.  Thus for declarer to succeed when back with the lead after playing low from dummy and losing to South's J would be play to Q !C if South started with J10 or play to A if South started with KJ.  Which is more likely?  Restricted choice tells us that with  !C J10 doubleton South would be just as likely to play the 10 as the Jack.  Whereas with KJ, South must play the J. ?????? Another consideration is "holes.  North-South did not come into the bidding so we cannot assume anything about suit length except perhaps that North's opening lead suggests at least 5 hearts.  This assumed  !H distribution negates the argument to allow for an extra hole in the South hand for the missing club.  However, we still come down to playing the A  !C (bringing down the King) as being twice as likely to succeed as finessing. 

End of story?  ???????  South is a top player who would play K from KJ doubleton, "knowing" that declarer will then take the supposed marked finesse and fail.  So after all we should finesse the Q  !C because we "know that South is too good a player to play  !C J from KJ.

Hmm!  Not sure if my analysis stands up.  Thanks for raising these questions Ken.

kenberg

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Re: Poco's Play Problems
« Reply #4 on: October 22, 2019, 08:03:57 PM »
There are various possibilities. Suppose N held T93 and S held KJ. So on the first club from the board S plays the J (I am not optimistic about going up with the K). N follows with the 3. Later declarer leads a small club from hand. It seems that N should play the T rather than the 9. If N plays the 9, declarer must decide whether S started with KJ or JT, and will consider that S could have played the T if he held JT, making KJ better than even odds. But if N plays the T on the second round then declarer has to decide between declarer holding AJ or J9.  The argument that he might have played the 9 from J9 is considerably weaker than the JT argument that occurs if N plays the T on the second round.

But wait! If we assume that N would play the T on the second round when dealt T93 then playing the 9 from T93 on the second round could convince declarer that N does not have the T, therefore S does.

There are a lot of possibilities, and I really am not sure just how it all works out.

The point of the hand was to give up a club early and certainly that's right. But the rest of it is some fun too. They are nice hands.
Ken

poco1

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Re: Poco's Play Problems
« Reply #5 on: November 05, 2019, 10:30:57 PM »
Hi again all!   The second session of "Poco's Play Problems" took place on Tuesday 5th November. Lots of kibs attended and it was decided to hold the event as a tourney in future. The next session will take place in a fortnight's time, on Tuesday November 19th at the same time. See IAC calendar for details. Don't worry about the bidding on the attached hands and commentaries. As pointed out before, these are PLAY problems and the bidding given is based on UK methods. Your own particular systems may well be different. I hope that you enjoy the hands.

Curls77

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Re: Poco's Play Problems
« Reply #6 on: November 06, 2019, 07:42:31 PM »
That was one excellent lesson, ty so much Colin for gifting us with ur time and knowledge :)
See yall in 2 weeks -- remember to sign up for trny and join review afterwards!

poco1

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Re: Poco's Play Problems
« Reply #7 on: November 19, 2019, 09:14:59 PM »
The latest set of hands were all about planning the play in No-Trump contracts. Some were more difficult that others, but everybody seemed to enjoy the challenges. The hands, and a brief commentary are available below. Join us again in a fortnight's time, on 3rd of December at the same time, for another set of brain-teasing problems. Enjoy your games!

poco1

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Re: Poco's Play Problems
« Reply #8 on: December 04, 2019, 07:14:35 AM »
The latest set of Poco's Play Problems were used in a tourney on 3rd December. The theme was "Suit Establishment." The next tourney and discussion will be on Tuesday 17th December... put it in your diary!  The latest hands, and a brief commentary describing the correct play are attached below. I hope that you enjoyed them!
« Last Edit: December 04, 2019, 07:16:21 AM by poco1 »

wackojack

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Re: Poco's Play Problems
« Reply #9 on: December 04, 2019, 06:40:44 PM »
You are in 4 !H and RHO leads K !D

 !S QJ6
 !H Q109
 !D A6
 !C J7642

 !S 843
 !H AKJ543
 !D 74
 !C AK
It is easy to see that if you draw trumps and lead towards dummy twice in spades you will make if both are with LHO or they are split.  (Line A say) This gives you a 75% chance.  A superior alternative is given:  Line B say
"Far more reliable is to establish the clubs, as long as the trumps do not break 4-0. Declarer wins the diamond lead, cashes the AK !C and crosses to dummy with 9  !H to ruff a club high. Back to dummy with 10  !H and ruff another club high. The Q  !H remains as an entry to the established club trick. If hearts were 4-0, declarer then  hopes for the favourable spade position."

Line B will fail when spades are favourable and if clubs split 5-1 or 6-0 and the "a priori" odds of this happening is 16%. So it appears that line B is fairly superior (84%) against 75%, but not by that much. 

However, as mentioned what about a 4-0 trump break?  It appears that line B is unaffected by a 4-0 trump break whereas as it says in the text line B is affected but when you find a 4-0 trump break you can revert to line A.  The odds of a 4-0 trump break is 9.6%.  I leave Ken the expert on stats to evaluate how much Line B advantage is eroded.  (I think only the odd percent).

I am posting this because I chose Line A.  I notice that only one pair chose Line B.  All others chose losing lines but got gifts from the defence. 

Just a theoretical mind game.  If odds of success by one course of action is 98%  and another is 99% then the 98% chance failure rate will be twice that of the 99% chance.  But we don't look at things in that way.  We just see a 1% difference. 

kenberg

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Re: Poco's Play Problems
« Reply #10 on: December 04, 2019, 09:14:15 PM »
I'll perhaps work through the probabilities later but there are interesting features.

For example, Lho has some sort of decent values in diamonds. If he had the !S AKx would he have started with the !D K? The auction began 1 H -2 !C. He might worry that declarer can pitch a spade loser on clubs right away unless he takes his spades.  If we decide that the lead makes it unlikely that Lho has !S AKx then that makes it more likely that Rho does. Maybe not a lot more likely, but perhaps a 30% chance rather than a 25 % chance.

There is also the complicating feature that the !C  might fall in two rounds.  Of course if it does, then line B will work just fine. Imagine for a moment it is matchpoints. Then, of the !C Q falls on the second round of clubs, we can make an over-trick if hearts are no worse than 3-1. Go to the board in hearts, ruff a small club high, draw trump ending on the board, cash the !C J and now the long !C is also good.

Added: I thought of another way that line B could work. Suppose that the !C AK brings down the Q and you lead a small heart to the board. Lho shows out. Rho has all four hearts. No problem. You lead the !C J from dummy. Rho must ruff, otherwise that is a tenth trick. So he ruffs and you over-ruff. Now he ans dummy both have two hearts left. Lead a heart to dummy and lead a club, ruffing.  There is now one club left in dummy, it good, a small heart to dummy draws the last trump, you cash the good club.

Here is an important point about mathematics that goes beyond bridge. Math is useful, very useful, it can allow you to draw conclusions from assumptions. But caution is needed. Often there is more to a situation than you at first think. Math can still be useful, it often is still useful, but there is a need for care.

All in all, it seems the recommended play of !C AK is the winner.

Often purely abstract probability arguments have to be modified by inferences from the play. In this case I think the modifications enhance rather than detract form the argument for line B.


« Last Edit: December 05, 2019, 12:09:19 AM by kenberg »
Ken

wackojack

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Re: Poco's Play Problems
« Reply #11 on: December 05, 2019, 09:54:55 AM »
Thanks for those very convincing observations Ken.  Yes the inferences from the K !D lead  convincingly increase the chances of line B over line A.  A good lesson for me.