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Daily Quiz 3/25

Posted By: kruidenbuiltje
Date: Tuesday, 3 April 2012, at 10:09 a.m.

In Response To: Daily Quiz 3/25 (Daily Quiz)

Daily Quiz 25 march 2012

Number 1

The split with 24/23 might not look too risky, but when you count the shots: white has 24/36 ways to start a blitz. His better board (with golden structure) makes his position good enough to double after 13/9 24/23. At an equal score blue would still have a take, but at 2a/5a it might be a pass.

After making the 5-point: 9/5 6/5, white has a slight positional advantage, but without a threat i don’t think it’s a double yet.

On top of this there are also flexibility considerations: making the 9-point strips the midpoint and doesn’t unstack the heavy 6- and 8-point.

Answer: 9/5 6/5

Number 2

The double-hit makes white a 60% favourite. A single hit with 18x15 8/4 gives white 19/36 returns, making him a favourite of about 47%. By not hitting but buttoning up his position blue has about 40% race-chance. Another factor to consider is that white misses his midpoint. This makes it harder to escape the two bar-anchored-checkers. Only D4 and D5 do this at once. Even with a huge amount of time (white has 61 free pips, that means he has 8,5 moves to throw a good double) he will leave a 6-shot about 65% of the time. So after the safe play blue is a slight favourite (about 60% = 40% race + 60% (no-race) x 65% (shot-chance) x 17/36 (6-shot-hitchance))

Answer: 8/4 6/3

Number 3

White is 15 pips ahead here. In positions with both sides having a high point open and a man on the bar the doubling window opens at 10 pips and closes at 5 pips. The differences with the reference position are mainly an advantage for blue. White has to enter on low points behind a 5-prime, blue has no prime to face after entering. Blue and white both have extra outfield control, but blue’s 8-point is the most valuable here since it’s 6-away from the main entry point (2) for white.

The above arguments seem enough to get this position into the doubling window, then there is the fact that white has 7 outfield crossovers, so that an eventual close-out may lead to 40% instead of the normal 5% gammons. Is this enough to make it a pass? I think it is close. Based on the score, I think it’s a narrow take.

Answer: DT

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