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BGonline.org Forums
Daily Quiz 3/30
Posted By: kruidenbuiltje In Response To: Daily Quiz 3/30 (Daily Quiz)
Date: Saturday, 7 April 2012, at 8:17 p.m.
Daily Quiz 30 march 2012
Number 1
The main choice here seems to be if we should stay or leave the anchor. Based on the race staying seems to be the best. The problem is that 13/3 8/3(2) gives an awkward stack on the 3-point, and awkward playability due to the stripped blue position. (As a matter a fact 61,51,31,21,62,52,32,63,53,D3 all play rather poorly) 13/3 13/8(2) solves the playability issue, but at the cost of giving white total control over the outfield. So now the choice is between moving the 5-anchor to the 10-point or the 15-point. The advantage of moving all the way to the 10-point is that it leaves a spare on the midpoint, which is good for playability, and the extra block on delta-3 can be useful. The only disadvantage seems to be that the moves 41,31, 43 and 64 become good for white. The advantages look bigger.
Answer: 20/10(2)
Number 2
With a racing chance of about zero blue needs to hit to win. He might try to increase contact with 13/4, which is often correct in cases where the opponent has a bad board. On first sight it seems to be a borderline case here. So lets try to calculate some things. After the safe 13/10 13/7 the shot quality is about 14/36 on average. The extra contact raises this number to about 20/36, but being hit makes only 63 and 53 re-hit, thus 4/36. Of the 22/36 numbers that leave shots, 6/36 do hit and 10/36 make use of the extra contact (the other 6/36 make no difference!).
Advantage: 10/36 (extra contact) x 6/36
Disadvantage: 6/36 (hits) x 10/36
Funny, we break-even.
Now the issue of white playing D1 or D2, is the extra contact advantegeous or disadvantegeous? The answer depends on blue entering or fanning. The average shot quality becomes 16/36 after entering on the 5-point, 24/36 after entering on the 6-point, and 5/36 after fanning. The weighed average of all this is 499/1296 and 11/36 = 396/1296. So, a plus of 2/36 x 103/1296 = 0,5% for the contact play, or we should simply conclude that white should not hit when he plays D1 or D2, at least not with D1, since this doesn’t influence the front position. So let’s say the advantage is 0,25%.
But then there are the gammons after hitting. After a hit and direct entry the gammonchance is about 11%, after the first fan it raises to 22% gammons. The average gammonchance is about 4%, so at the end the extra contact doesn’t pay off. But since it’s rather close it is very possible that a small shift (like moving the 15 point back to the 16-point) might make it correct.
Answer: 13/7 13/10
Number 3
Here we have the choice between the safe 16/8 or 16/10 13/11, the last move unstacks the midpoint and gives extra builders for the 4,7,9 and 10-point. The risk is relatively low because of the many happy returns, the effective risk is about 5/36. The problem however is that blue might not need the extra points, since he is already favourite.
Maybe it’s more important to see how many awkward moves the safe play gives: 65,63 and 54 all leave a direct hit (extra risk = 6/36 x 11/36 = about 2/36), after 16/10 13/11 there are no blot leaving blue moves.
The extra risk of the risky play is only 5/36 – 2/36 = 3/36. The reward is high since blue is a favourite to make a 4-prime. Not being hit gives blue a double/pass.
Answer: 16/10 13/11
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