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2012 Osaka Open Quiz

Posted By: Taper_Mike
Date: Monday, 26 March 2012, at 4:02 a.m.

In Response To: 2012 Osaka Open Quiz (kinchan)

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Thanks for sharing this most entertaining set of problems from the 2012 Osaka Open. Mike

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White is Player 2 score: 9 pip: 4 11 point match pip: 15 score: 8 Blue is Player 1 XGID=----AAA--------------a----:1:-1:1:12:8:9:0:11:10 Blue to play 12

Problem 1 After this turn, Blue will get another roll only when White rolls 21 on his turn. Then, Blue will need to roll a doublet to win. If Blue makes the 3pt now, he can win next turn with 33, 44, 55 and 66. No other play does as well. Answer:– 5/3– 4/3

Problem: – 01 – 02 – 03 – 04 – 05 – 06 – 07 – 08 – 09 – 10

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White is Player 2 score: 5 pip: 3 7 point match pip: 46 score: 4 Blue is Player 1 XGID=-EEC--A---------A-------c-:0:0:1:21:4:5:0:7:10 Blue to play 21

Problem 2 As in Problem 1, Blue will have at most one more turn to save the gammon. On this turn, he must arrange his checkers to maximize the number of rolls of doublets that will bear off a checker on the next turn. By playing to the 13pt, Blue can save the gammon when he rolls 33, 55 and 66. But when he plays 16/15 6/4, he also beats the gammon with 44. Answer:– 16/15– 6/4

Problem: – 01 – 02 – 03 – 04 – 05 – 06 – 07 – 08 – 09 – 10

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White is Player 2 score: 0 pip: 108 3 point match pip: 38 score: 0 Blue is Player 1 XGID=-bDBF--a-----------bbbbbb-:1:-1:1:12:0:0:0:3:10 Blue to play 12

Problem 3 White needs a minimum of 49 pips to save the gammon. That’s almost exactly 6 “average” rolls. Blue, meanwhile, still has 12 checkers to bear off. At two checkers a turn, that is also 6 rolls. Because the gammon is close, Blue should bear off aggressively. Rip one now, instead of playing two from the 4pt. The risk is minimal. Answer:– 4/3– 2/off

Problem: – 01 – 02 – 03 – 04 – 05 – 06 – 07 – 08 – 09 – 10

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White is Player 2 score: 2 pip: 131 5 point match pip: 122 score: 0 Blue is Player 1 XGID=-aaD-AD-D---b-a-a--bbbbaAA:1:1:1:11:0:2:0:5:10 Blue to play 11

Problem 4 Two aces seem certain: Bar/24 and 6/5. After that, making either the 2pt, 7pt or 23pt will be the other two aces. Right away, Blue should reject making the 7pt. It makes a nice block, but at this juncture, Blue must hit. The 2pt seems far the best target. It hits, yes, but it also adds a fourth innner-board point at a time when dancing could be fatal for White. Furthermore, Blue will have trouble making a point later with his dilly builders on the 3pt. This is a great opportunity to put them to use. If White had more checkers in the zone, Blue could consider making the 23pt before White managed to grab it, but not here. Answer:– Bar/24– 6/5– 3/2*(2)

Problem: – 01 – 02 – 03 – 04 – 05 – 06 – 07 – 08 – 09 – 10

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White is Player 2 score: 0 pip: 86 1 point match pip: 94 score: 0 Blue is Player 1 XGID=aBCE--B---a-----aA-bbBbcc-:0:0:1:63:0:0:0:1:10 Blue to play 63

Problem 5 Blue needs to leave a checker in direct range of White’s blot on the 10pt. Otherwise, White may enter, and pick up the blot on the 16pt. That would leave Blue only with indirect shots from the anchor on his 21pt to hit a blot that would be 11 pips away. Once you realize that, duplication does the rest. 21/15 17/14 very nicely duplicates the 4s and 5s that White needs to enter. Answer:– 21/15– 17/14

Problem: – 01 – 02 – 03 – 04 – 05 – 06 – 07 – 08 – 09 – 10

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White is Player 2 score: 2 pip: 128 5 point match pip: 167 score: 0 Blue is Player 1 XGID=--a-A-DAC---bBa--bceC-A-a-:1:1:1:14:0:2:0:5:10 Blue to play 14

Problem 6 It is hard to find a good play here. Making the 3pt is safest, but seems like the first step on the road to second place. Making the 4pt, and then playing a rear checker up, allows White the opportunity to escape with tempo when he rolls a 5. Crazy plays, such as making the 4pt, while slotting the 5pt, don’t seem to be called for. A more balanced move is 20/16 8/7. It duplicates 2s, and should White hit with a 4, he must break his midpoint. The extra blot in the outfield will also give Blue more coverage should White try running. Answer:– 20/16– 8/7

Problem: – 01 – 02 – 03 – 04 – 05 – 06 – 07 – 08 – 09 – 10

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White is Player 2 score: 0 pip: 112 Unlimited Game Jacoby Beaver pip: 142 score: 0 Blue is Player 1 XGID=-a--BBCbBC--------bccC-ac-:0:0:1:26:0:0:3:0:10 Blue to play 26

Problem 7 Blue need not fear getting hit here. What he should fear is losing control of the outfield. White is threatening jump out with a 6, and then have a free run through the outfield. This, at a time when White leads by 30 pips. Although I am not sure the answer is the same, I saw a somewhat similar position at Bill Robertie’s Two-Plus-Two Forum last month. Uncertain as I am, I’ll try the same reply nevertheless. Coming to the midpoint duplicates White’s 6s, and when White hits, White immediately opens the door to losing a gammon. When White does not hit, Blue will have the choice of making the midpoint, and entering a much more favorable holding game, or else bringing another builder down to threaten in the inner board. Answer:– 21/13

Problem: – 01 – 02 – 03 – 04 – 05 – 06 – 07 – 08 – 09 – 10

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White is Player 2 score: 0 pip: 68 Unlimited Game Jacoby Beaver pip: 109 score: 0 Blue is Player 1 XGID=-ABBBBB-----bB-----c-Beda-:1:1:1:44:0:0:3:0:10 Blue to play 44

Problem 8 Were White’s board threatening, I would play 21/17(2) 13/9(2). With so little to fear, I prefer to provoke some action. Answer:– 21/5

Problem: – 01 – 02 – 03 – 04 – 05 – 06 – 07 – 08 – 09 – 10

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White is Player 2 score: 1 pip: 130 5 point match pip: 126 score: 1 Blue is Player 1 XGID=-a----EaDBB-bB---bbd-a-b--:1:-1:1:44:1:1:0:5:10 Blue to play 44

Problem 9 Owning seven points is usually indicative of an over-stretched position, so the obvious 8/4(2) 6/2(2) is not overly attractive. Still, it gives Blue an instant three-point board, and he might win in an attack after that. For similar reasons of inflexibility, making the 4pt and 5pt does not promote safe play in the turns that follow. The most flexible play, 13/9(2) 6/2(2), has the drawback of making the 2pt. Filling in the gaps would require some precise rolling. I like the simple play. Make the 5pt. As they say, even if you are wrong, you won’t be wrong by much. Answer:– 13/5(2)

Problem: – 01 – 02 – 03 – 04 – 05 – 06 – 07 – 08 – 09 – 10

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White is Player 2 score: 6 pip: 6 11 point match pip: 99 score: 10 Blue is Player 1 XGID=---BBCF---A------------cA-:1:1:1:64:10:6:0:11:10 Blue to play 64

Problem 10 This one is all about the score. In a money game, and supposing Blue had a prime instead of just a four-point block, Blue would stay back, hoping to win the coup classique. At this score, however, losing a backgammon will cost him the match. Over the board, best might be to do no more thinking than this, and quietly play the 6 out to the 18pt. Having done that, Blue must next determine whether he can save the gammon. He will have at most only one more turn. Moving either outside checker with the 4 will let him save the gammon with 44, 55 and 66. No other move does better. By this play, Blue is resigning himself to playing the DMP game, with Match Winning Chance (MWC) = 50%, except when the follow parlay occurs: 1. White does not bear off all three checkers on his turn (31/36), 2. Blue saves the gammon on his roll (3/36). Thus, with probability 93/1296, Blue can reach the match score 1-away, 3-away (post Crawford). From there his MWC is 68%. Blue’s overall MWC will be (93/1296) * 68% + (1203/1296) * 50%, or about 51%. Can he do better by staying back now? 5/36 — If he does, he will lose the match immediately when White bears off all three checkers. – 1/36 — When White rolls 11, Blue will have no chance to hit, but will lose a backgammon when his own roll totals 6 or less. Should he be lucky enough to roll 7 or more, he will lose a certain gammon. – 10/36 — On ten rolls (any ace except 11), Blue will get a double shot from the bar. These are the variations that give Blue a legitimate chance to win. Even when he does not win, he will often save the gammon. Of course, if Blue misses the double shot, as he will 16 times in 36, he will lose a gammon. – 20/36 — With the twenty other rolls, Blue will get a single shot from the ace point. In this latter case, even when Blue is able to hit, and close out White’s remaining checker, Blue’s Game Winning Chance (GWC) is only about 8.5%. In this game, where Blue has only a four-point block, Blue will win less often, say 1 time in 20. Once again, even when he loses the game, Blue will save many gammon losses when he hits the shot. These considerations sketch out the beginning of a calculation that would give a fairly accurate estimate of Blue’s MWC when he stays back. I have already written too much, however, so I will leave it to someone else to complete. For the quiz, I will stay with my over-the-board determination. Answer:– 24/18– 10/6

Problem: – 01 – 02 – 03 – 04 – 05 – 06 – 07 – 08 – 09 – 10

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Messages In This Thread

• 2012 Osaka Open Quiz
  kinchan -- Saturday, 24 March 2012, at 9:13 a.m.
  • 2012 Osaka Open Quiz
    Sam Pottle -- Saturday, 24 March 2012, at 11:31 p.m.
  • 2012 Osaka Open Quiz
    Taper_Mike -- Monday, 26 March 2012, at 4:02 a.m.
    • Answer : Don't click before think the quiz :-)
      kinchan -- Monday, 26 March 2012, at 1:05 p.m.
      • Answer : Don't click before think the quiz :-)
        kinchan -- Monday, 26 March 2012, at 1:27 p.m.