Small problem... Error in the answer ?

[etherwill]

Hi, I was recently offered Volume 4 from the books "Graded go problems for beginners".
However, I don't understand the answer given by the book for problem #4. I hope someone here can enlighten me

THe first diagram presents the problem, the second one is the answer provided by the book.

$$c Problem.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . X . O O O . . . . . . . . . . . . . |
$$ | . . . O X X X X . . . . . . . . . . . |
$$ | . X X X O O . . X . . X X . . . . . . |
$$ | . O . O X . O . . X . . . . . , . . . |
$$ | . . O O . . . . O O O . X . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$c Problem.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . X . O O O . . . . . . . . . . . . . |
$$ | . . . O X X X X . . . . . . . . . . . |
$$ | . X X X O O . . X . . X X . . . . . . |
$$ | . O . O X . O . . X . . . . . , . . . |
$$ | . . O O . . . . O O O . X . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

$$c Answer, the book states that after 5, white has to give up the two stones in atari.
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . X . O O O . . . . . . . . . . . . . |
$$ | . . . O X X X X . . . . . . . . . . . |
$$ | . X X X O O 5 . X . . X X . . . . . . |
$$ | . O . O Y a O 1 . X . . . . . , . . . |
$$ | . . O O . . 2 3 O O O . X . . . . . . |
$$ | . . . . . . . 4 . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$c Answer, the book states that after 5, white has to give up the two stones in atari.
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . X . O O O . . . . . . . . . . . . . |
$$ | . . . O X X X X . . . . . . . . . . . |
$$ | . X X X O O 5 . X . . X X . . . . . . |
$$ | . O . O Y a O 1 . X . . . . . , . . . |
$$ | . . O O . . 2 3 O O O . X . . . . . . |
$$ | . . . . . . . 4 . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

What I don't understand is that if white plays at a, then the triangled stone is in atari. If I try to go on, I get something which looks like this :

$$c cont'd.
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . X . O O O . . . . . . . . . . . . . |
$$ | . . . O X X X X . . . . . . . . . . . |
$$ | . X X X O O 5 . X . . X X . . . . . . |
$$ | . O . O Y 6 O 1 . X . . . . . , . . . |
$$ | . . O O 7 8 2 3 O O O . X . . . . . . |
$$ | . . . . 9 . 0 4 . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$c cont'd.
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . X . O O O . . . . . . . . . . . . . |
$$ | . . . O X X X X . . . . . . . . . . . |
$$ | . X X X O O 5 . X . . X X . . . . . . |
$$ | . O . O Y 6 O 1 . X . . . . . , . . . |
$$ | . . O O 7 8 2 3 O O O . X . . . . . . |
$$ | . . . . 9 . 0 4 . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

I thought of 9 at 10, but then of course, 7 and the triangled stone are atari, so white seems out of danger. Even better, 9 is useless, isn't it ?
Is there an error somewhere, in the book or in my head ?

[amnal]

White can save the two stones in atari, but black and add up to an even worse loss for white. Black has destroyed way more than 4 points of territory (which was the value of the 2 stones), plus the 3 white stones on the right are captured - that is, they have no way to run away as black has cut them off.

$$c
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . X . O O O . . . . . . . . . . . . . |
$$ | . . . O X X X X . . . . . . . . . . . |
$$ | . X X X O O 5 . X . . X X . . . . . . |
$$ | . O . O Y 6 O 1 . X . . . . . , . . . |
$$ | . . O O 8 . 2 3 O O O . X . . . . . . |
$$ | . . . . . . 7 4 9 . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$c
$$ ---------------------------------------
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . X . O O O . . . . . . . . . . . . . |
$$ | . . . O X X X X . . . . . . . . . . . |
$$ | . X X X O O 5 . X . . X X . . . . . . |
$$ | . O . O Y 6 O 1 . X . . . . . , . . . |
$$ | . . O O 8 . 2 3 O O O . X . . . . . . |
$$ | . . . . . . 7 4 9 . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

[etherwill]

Ok, thanks, fast reply !
I didn't see things that way, although I went through this variation... But I wanted too much to kill the white groups !

[frankie99]

I wouldn't recommend doing that volume of the graded go problems for beginners series unless you a single digit kyu.

ramble:

The range of ranks printed on the books is way way off.
you can find more info here: http://senseis.xmp.net/?GradedGoProblemsForBeginners
and in david carlton's review: http://www.gobooks.info/h3.html, he mentions an ad.

(Recent ads for these books have them at 30-25 kyu, 25-15 kyu, 15-8 kyu, and 8-3 kyu; that seems reasonable to me.)

you can spend a day or two while in the corresponding range to finish volumes 1-3. For volume 4 i think you should wait until you are atleast a 5k. Of course, if you know vol 1-3 really really really well u can start early i guess. Just don't expect to finish the volume in a couple of days even if you are a 5k.

Good Luck

[etherwill]

Yep... As I said before, it was a present, I didn't get to pick the book
But thanks for the heads up