[zasanya]

Suppose you are declarer and you have Kxx in one hand AJ109xx in the other .We are always taught '8 ever 9 never'. But what are the exact percentages in favour of finesse or drop? Will the % change if we decide to run the Jack without cashing Ace?

[gwnn]

2-2 is 40%
3-1 is 50%
4-0 is 10% (note that these are simple percentages, you can apply them at the table if you want).

1) drop wins with all 2-2's (queen drops 40%), a quarter of 3-1's (queen is singleton +12.5%=52.5%) and a half of 4-0's (you will finesse twice if Qxxx is onside assuming you have enough transportation etc 52.5%+5%=57.5%) 57.5% of the time.
2) finesse (K then small to jack) wins with half the 2-2's (20%), half the 3-1's (Qxx onside: +25%=45%), one-eights of the 3-1's (singleton Q offside: +6.25%=51.25%) and half the 4-0's (+5%=56.25%), or 56.25% of the time.
3) finesse (A then run jack) wins the same as above except the 4-0's so 51.25%.
4) finesse (just run jack or just small to jack) wins the same as 2 but you lose the singleton Q offside case so it is 50.00%.

1 and 2 are not that far off so you can/should finesse if you have any reasonable inference in its favour.

[Antrax]

<edit: see percentages above>
In any case, one trick you might want to know is if you decide to play for the drop from that holding, lead the J towards the K - against "cover honor with an honor" opponents that lets you pick up half of the 3-1 and 4-0 splits.

[FrancesHinden]

This is getting very off topic, but this is one of my favourite suit combinations. If you are in a NT contract, how do you play

AJ109x

opposite

Kxxx

if dummy has no entry and you have bid e.g 2NT - 3NT

[mikeh]

FrancesHinden, on 2012-January-16, 16:27, said:

This is getting very off topic, but this is one of my favourite suit combinations. If you are in a NT contract, how do you play

AJ109x

opposite

Kxxx

if dummy has no entry and you have bid e.g 2NT - 3NT

which one is dummy? I assume Kxxx but maybe I'm wrong...I'd estimate I'd be wrong 56.75% of the time

[FrancesHinden]

Sorry, the full hand is something like this:


xxx
xx
xxx
AJ109x

AKx
Ax
AKxx
Kxxx

you bid 2NT - 3NT at matchpoints and get the queen of hearts lead, RHO encourages but you don't know the count.

[Phil]

FrancesHinden, on 2012-January-16, 16:42, said:

Sorry, the full hand is something like this:


xxx
xx
xxx
AJ109x

AKx
Ax
AKxx
Kxxx

you bid 2NT - 3NT at matchpoints and get the queen of hearts lead, RHO encourages but you don't know the count.

Reminds me of a certain article in the Bridge World a few years ago

[BillHiggin]

zasanya, on 2012-January-16, 02:09, said:

Will the % change if we decide to run the Jack without cashing Ace?

This question brings up a B/I type issue (Csaba surely never would even consider cashing the Ace first since experts immediately know that the King is the correct honor). Cashing the Ace first will lose to both 4-0 splits since you now have lost the chance to finesse twice. The two options to finesse before cashing either honor are also unequal - leading the Jack towards the King will pick up either 4-0 split but leading towards the Jack will only pick up one of them. In fact, leading the Jack towards the King with the intention of letting it ride is better than cashing the Ace first.

Exact percentages are seldom really useful - at the table there is usually some additional information. But assuming that the only real information available is limited to the opening lead and the card played by RHO to that trick (and assuming the long suit is in declarer's hand for simplicity purposes), precise numbers would be:
1a] Cash King then the Ace - 58.1%
2] Cash King then finesse - 56.2%
4a] Hook LHO immediately - 54.7%
1b] Cash Ace then the King - 53.4%
3] Cash Ace then finesse - 51.6%
4b] Hook RHO immediately - 50.0%

[gwnn]

BillHiggin, on 2012-January-16, 18:44, said:

This question brings up a B/I type issue (Csaba surely never would even consider cashing the Ace first since experts immediately know that the King is the correct honor). Cashing the Ace first will lose to both 4-0 splits since you now have lost the chance to finesse twice. The two options to finesse before cashing either honor are also unequal - leading the Jack towards the King will pick up either 4-0 split but leading towards the Jack will only pick up one of them. In fact, leading the Jack towards the King with the intention of letting it ride is better than cashing the Ace first.

Exact percentages are seldom really useful - at the table there is usually some additional information. But assuming that the only real information available is limited to the opening lead and the card played by RHO to that trick (and assuming the long suit is in declarer's hand for simplicity purposes), precise numbers would be:
1a] Cash King then the Ace - 58.1%
2] Cash King then finesse - 56.2%
4a] Hook LHO immediately - 54.7%
1b] Cash Ace then the King - 53.4%
3] Cash Ace then finesse - 51.6%
4b] Hook RHO immediately - 50.0%

why was my 57.5 (among others) wrong? is it because it's not 40-50-10 exactly or because I messed up my algebra?

[bluecalm]

Quote

you bid 2NT - 3NT at matchpoints and get the queen of hearts lead, RHO encourages but you don't know the count.

Playing small to the jack can never work against good defenders imo (cause RHO knows LHO would play the king from Kxx/Kx so I don't see anything. Awaiting the reveal

[BillHiggin]

gwnn, on 2012-January-18, 03:20, said:

why was my 57.5 (among others) wrong? is it because it's not 40-50-10 exactly or because I messed up my algebra?

"Wrong" is much too strong a word here. Both your figures and mine are probably written with too much precision. Your 40-50-10 figures are certainly great for "at the table" math, but really represent single digit accuracy. Two digit accuracy would be 41-50-9. Adding another decimal point would be about 40.7-50.0-9.3 but then other inferences really become significant.

If we round off properly to two digit percentages then your 58% and my 58% are no longer different! I would certainly use the 40-50-10 figures when I did not have access to a high powered computer.

[gwnn]

Sure. I was just curious where the difference came from. Now I looked them up and it's 40.7-49.7-9.6 anyway I agree that "wrong" was a silly word to use

further reading (it's kind of a funny thread but also somewhat sad):
http://www.bridgebas...-declarer-play/

[FrancesHinden]

bluecalm, on 2012-January-18, 03:31, said:

Playing small to the jack can never work against good defenders imo (cause RHO knows LHO would play the king from Kxx/Kx so I don't see anything. Awaiting the reveal

You play small to the ace and run the jack. A good LHO would often put in the Q from Qx or Qxx for exactly the same reason as from Kx or Kxx


Phil depressed me by telling me this has already been written up in BW. I worked this out for myself in a local league match once when the auction was 1NT all pass, dummy was exactly as in my example, and at both tables the queen was inserted from Qxx which let the contract through.

[kuhchung]

FrancesHinden, on 2012-January-19, 16:29, said:

You play small to the ace and run the jack. A good LHO would often put in the Q from Qx or Qxx for exactly the same reason as from Kx or Kxx


Phil depressed me by telling me this has already been written up in BW. I worked this out for myself in a local league match once when the auction was 1NT all pass, dummy was exactly as in my example, and at both tables the queen was inserted from Qxx which let the contract through.

I was completely stumped for a while until my friend told me, "it depends on your LHO." Then it dawned on me and I couldn't stop laughing. Thanks for sharing.