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Add one White King and one White Queen and as many Black Queens as possible to the board so that White can mate Black in a single move. Also give the checkmating move.

Clarifications:

  • After the pieces are placed on the board, it is White’s turn to play.
  • You can’t place multiple pieces on a single square.
  • You can’t place any pieces other than the ones mentioned above.
  • For this puzzle, you can place more than 9 Black Queens.
  • After White’s single move, Black is checkmated and White is not in check.

EDIT: Although I didn’t originally state it, my intention was that all the rules of Chess apply in this puzzle except for having more than 9 Queens.

2nd EDIT: When I originally posted this puzzle, I had intended that the Black King’s position was fixed. Since I didn’t originally mention this, I will consider answers that relocate the Black King to any starting position.

Standard chessboard empty except for a Black King on square d5

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4 Answers 4

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I was able to find one with 36 queens (Edit : This is if we can place the black king anywhere, OP wants the position of black king to be fixed on d5)

36 queens



UPDATE : A solution with 33 Black queens, with black king on d5 (Switching White queen from c4 to c6 also gives 33 Black queens)

33 Queens

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  • 1
    $\begingroup$ Welcome to puzzling SE! $\endgroup$ Commented Oct 2 at 2:34
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    $\begingroup$ Could add one more black queen on b7, I think? $\endgroup$ Commented Oct 2 at 2:42
  • $\begingroup$ @Jafe You're right! I didnt consider capturing a queen with the last move, that moves the number of queen to 37 $\endgroup$ Commented Oct 2 at 2:48
  • $\begingroup$ @Will.Octagon.Gibson Ah, I guess I missunderstood the question, didn't know the black king's position is fixed, my bad. $\endgroup$ Commented Oct 2 at 2:57
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    $\begingroup$ @Will.Octagon.Gibson The best I could find was 33 (34 if we consider black queen on c4 which queen captures) $\endgroup$ Commented Oct 2 at 3:21
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32 black queens cannot save their king. Qc6# wins for white.
32 queens can't save their king

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  • $\begingroup$ Moving the white king to d7 allows for one more black queen. $\endgroup$ Commented Oct 1 at 23:27
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    $\begingroup$ Doesn't wK on a8 and bK on c6 give us 35 queens? $\endgroup$ Commented Oct 2 at 1:46
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    $\begingroup$ @kagami I had a different solution with 35 queens, but realized that the puzzle was intended to have the black king on D5. $\endgroup$ Commented Oct 2 at 9:59
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I'm terrible with this type of puzzle and will probably end up deleting this, but I'll go with this:

enter image description here

Each black "dot" can be a black queen.

The white queen can be anywhere that can reach d6 in one move.

That's 30 black queens.

(The checkmate move is Qd6).

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    $\begingroup$ Even though this is not an optimal solution, I encourage you to not delete it. $\endgroup$ Commented Oct 2 at 6:15
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Using the setup in the question, we can get

34 black queens

solution

K is the location of the white king, Q0 is the starting location of the white queen, and Q1 is where the white queen moves on white's turn. In order for it to be checkmate, neither of the white pieces may be threatened, so no black queens can be on the spaces marked with blue lines. If every space without a blue line has a black queen (represented by red dots and lines), then the black king cannot retreat.

Here's another option which achieves the same number of queens.

enter image description here

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  • $\begingroup$ In both of your configurations, it is not checkmate because the check can be blocked. Please try again. $\endgroup$ Commented Oct 3 at 3:05
  • $\begingroup$ @Will.Octagon.Gibson Oh, right. $\endgroup$ Commented Oct 3 at 3:19

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