Problem Answers

Problem 1

Black to play and capture three stones.
Black 1 threatens the three stones with immediate capture.
White 2 captures one black stone.
Black 3 captures four white stones. This is known in English as a snap-back.

This is not forbidden by the ko rule. Black has played on a point from which he has just had a stone captured; but the position is now different from what it was before White's previous move, so the position is not repeated, and this move is allowed.

Problem 2

White to play and capture five stones.
White 1 threatens the five stones with immediate capture.
Black 2 is the only way to avoid immediate capture.
White 3 now threatens seven stones with immediate capture.
Black 4 is again the only way to avoid immediate capture. It captures one white stone, making one eye.
White 5 threatens all eight black stones with immediate capture. There is nothing Black can do to avoid this. White will be able to capture them with her next move.

Problem 3

Where should Black play to guarantee two eyes for the black stones?
Black should play at 1. Then he has two eyes, one at a and the other at b.
Where should White play in order to kill the Black group?
White can play at a, b or c. Any one of these moves is enough to guarantee that the black group is dead.

Problem 4

Black to play and capture three stones.
Black must try to capture the group marked with triangles. That group has only two liberties. The other group of three white stones has five liberties, and it is not possible to capture it.
Black starts with 1, which threatens immediate capture.
White plays 2 to try to save her stones.
Black plays 3, which threatens immediate capture.
White plays 4 to try to save her stones.
Black plays 5, which again threatens immediate capture. (He could also play at a. That would work too.)
White plays 6 to try to save her stones.
Black plays 7, which again threatens immediate capture. This time, White has no way to avoid capture on the next move.
For Black to start like this is a mistake.
White is forced to save her stones with 2.
Now the best Black can do is to threaten them again with 3.
But now White captures a stone with 4. This connects her two groups together, and makes them secure.


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