1. Joined
    12 Mar '03
    Moves
    37225
    06 Dec '05 12:53
    For beginners only:

    Black to play. Indicate two moves (amongst other moves) that black MUST have played before.

  2. Joined
    01 May '05
    Moves
    390
    06 Dec '05 13:421 edit
    Originally posted by Mephisto2
    For beginners only:

    Black to play. Indicate two moves (amongst other moves) that black MUST have played before.

    [fen]rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBN1 b Qkq - 0 1[/fen]
    Nxh1; Ng3?
  3. Joined
    12 Mar '03
    Moves
    37225
    06 Dec '05 13:46
    Originally posted by fetofs
    Nxh1; Ng3?
    No. Why not?
  4. Joined
    08 Feb '05
    Moves
    13312
    06 Dec '05 14:341 edit
    The white knight on g1 could have come out and the rook could have been taken on this square?

    Edit: meant to reply and quote, this was in answer to "why not?"
  5. Joined
    12 Mar '03
    Moves
    37225
    06 Dec '05 14:491 edit
    Originally posted by nickhawker
    The white knight on g1 could have come out and the rook could have been taken on this square?

    Edit: meant to reply and quote, this was in answer to "why not?"
    Replace 'could have' with 'must have'.
    Black is on the move, he made an even number of moves, all knight moves, allowing them to go back to their original position.
    Hence, white made an odd number of moves, consisting of an even number of knight moves, and an odd (at least one) number of rook moves. The rook on a1 can only have made an even number of moves, hence, the rook on h1 must have made an odd number of moves, and was captured on g1.
    The capture was Nh3xRg1 because the knight would have harassed the white king from f3. And the knight must have gone back via h3: Ng1-h3 for the same reason.

    edit: typo's
  6. Joined
    01 May '05
    Moves
    390
    06 Dec '05 15:45
    Originally posted by Mephisto2
    Replace 'could have' with 'must have'.
    Black is on the move, he made an even number of moves, all knight moves, allowing them to go back to their original position.
    Hence, white made an odd number of moves, consisting of an even number of knight moves, and an odd (at least one) number of rook moves. The rook on a1 can only have made an even number o ...[text shortened]... from f3. And the knight must have gone back via h3: Ng1-h3 for the same reason.

    edit: typo's
    I thought about that, but I didn't try enough...
  7. SubscriberBigDoggProblemonline
    The Advanced Mind
    bigdogghouse.com/RHP
    Joined
    26 Nov '04
    Moves
    117330
    06 Dec '05 17:24
    Originally posted by fetofs
    I thought about that, but I didn't try enough...
    It's best on these type of problems to play out the game and verify the moves do happen.
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