Beginner Exercise 107 / Solution

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Solution

[Diagram]

Ko

After W1, B2 can make ko. W3 threatens a snapback.

The difference between winning and losing this ko is 19 points of territory. If Black wins he gets only 4 points of territory, while if White wins she gets 15 points.


Failure 1

[Diagram]

Black lives

If W1 here, then B2 lives as per rectangular six. Subsequently, a and b are miai for life.


Failure 2

[Diagram]

Larger ko

The difference between winning and losing this ko is 20 points, since Black gets 5 points if he wins it. W3 gives up a possible point for nothing.


[Diagram]

White wins the ko

White wins the ko in an unusual way with W7. Now if Black takes the ko, White captures the black+circle stones. It would be a mistake for White to fill the ko, because that just leads to another ko.


Real game

[Diagram]

Gote

W1 is gote, gaining 0.5 point more than the ko. You can see that because if Black wins the ko he gets only 4 points, but if he plays B1 first, he gets 5 points.



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