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Your grandfather and grandmother are playing chess, and you are sitting in the same room doing your own thing. A wide grin comes across your grandfather's face, and you can tell he is about to checkmate. Unfortunately, as he is reaching for the piece, he gets an important call on his phone. He asks you to take over his game for him. "You can checkmate on this move," he says. "Her knight would be able to block your queen, but it's already blocking the other one. Don't worry about her pawns, they're more of a hindrance than a help to her." He begins to walk away. "What a close game," he mumbles. "Same number of pawns... in fact, same number of pieces! Hm..."

Unfortunately, you are only five years old, and when you slide into your grandfather's chair at the large, tall table, your eyes are level with the chessboard and all you can see is:

enter image description here

What misfortune! Unfortunately, you know that all pieces are the same height (except for the pawns, which are shorter) so some pieces could be blocking your view of others behind them. Your grandmother, upon realizing your enigma, begins to cackle fiendishly. She does, however, tell you that there are exactly 8 pieces on the board.

What does the board look like? What move should you make?

NOTE: When I created this puzzle, I did not find all possible solutions, so there may be more than one. Also, "same number of pieces" does not mean the same number of each type of piece.

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    $\begingroup$ I need a set with knights that look like this. $\endgroup$
    – Rubio ♦
    Jun 14, 2017 at 19:50
  • $\begingroup$ Grandmother must have two pawns for the "Don't worry about her pawns, they're more of a hindrance" line to be sensible. That means Grandfather must have two pawns also. Each of course also has a King. That accounts for six pieces. The final two pieces on the board must be the White Queen and the Black Knight we see in the picture. That means the picture we see shows the four primary pieces already, and the only pieces not visible are the extra pawn each player must have. Am I understanding the puzzle statement correctly here? $\endgroup$
    – Rubio ♦
    Jun 14, 2017 at 22:47
  • $\begingroup$ Yes, your logic is sound, and that is consistent with the puzzle. :) $\endgroup$
    – Franklin Pezzuti Dyer
    Jun 14, 2017 at 22:51
  • $\begingroup$ This is a great puzzle. But you say all the pieces apart from the pawns are the same height. Since the black king appears taller than the black knight, which looks taller than the white king, which looks a lot taller than the white queen, I assumed that in order of increasing distance from white's first rank these pieces were arranged in that order. $\endgroup$
    – user36946
    Jun 15, 2017 at 8:17

2 Answers 2

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Grandmother must have two pawns for the "Don't worry about her pawns, they're more of a hindrance" line to be sensible. That means Grandfather must have two pawns also. Each of course also has a King. That accounts for six pieces. The final two pieces on the board must be the White Queen and the Black Knight we see in the picture. That means the picture we see shows the four primary pieces already, and the only pieces not visible are the extra pawn each player must have.

Here's a solution:

enter image description here

"You can checkmate on this move," he says.
Yup.

P=Q#

"Her knight would be able to block your queen, but it's already blocking the other one."

Black's Knight is pinned by White's queen on g5, preventing it from Nc6 to block the check by White's promoted queen. So it could block White's queen (the new one) but it's already blocking the other (queen).

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  • $\begingroup$ Yes, this is the answer I had (but shifted a little bit). Nice job! $\endgroup$
    – Franklin Pezzuti Dyer
    Jun 14, 2017 at 23:12
  • $\begingroup$ Cool puzzle. Solving that was fun :) $\endgroup$
    – Rubio ♦
    Jun 14, 2017 at 23:13
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    $\begingroup$ That's great, but it doesn't explain how the 5yo is supposed to actually play the winning move at the other end of the board with his tiny arms. $\endgroup$
    – Evargalo
    Oct 19, 2018 at 11:09
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This is one way to do it, assumption is that 'equal number of pieces, and equal pawns' means equal numbers of each piece.

two pawns, two knights, rook, and queen Winning move is QE4#

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  • $\begingroup$ It does not mean equal numbers of each piece... it means the same number of pieces in all. $\endgroup$
    – Franklin Pezzuti Dyer
    Jun 14, 2017 at 21:17
  • $\begingroup$ There should only be 8 pieces, no? $\endgroup$
    – Arthur Dent
    Jun 14, 2017 at 21:58
  • $\begingroup$ @Nilknarf is using "piece" to include pawns. That confused me at first, but he makes the meaning clear when he says that all pieces are the same height "except for the pawns". $\endgroup$
    – user36946
    Jun 15, 2017 at 8:21
  • $\begingroup$ This answer actually predated edits to the question, the eight-piece rule wasn't specified at the time, and I made a mistaken assumption about the piece distribution. $\endgroup$
    – Sconibulus
    Jun 15, 2017 at 13:00

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