Deductive Puzzle #5

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Avatar of TheGrobe
dsarkar wrote:
WanderingWinder wrote:
dsarkar wrote

N could not have been a promoted piece (white's K was at e1 last move) and at f1 must have captured something there or at e3. total 6 captures accounted for so far.


1st of all, how do you know that white's K was at e1 last move. Furthermore, why did the knight have to capture something on f1 or e3?


white's last move was either 0-0-0 or by the missing piece at g4 - K move from check of immobile B not possible. Now if there is a missing white piece at g4, then neither of the N, B(h2), Q has captured anything - which means black B went to h2 first, then white played g3, then the white B somehow managed to enter to h1, and the black Q followed the white bishop all the time exposed to its attack to g2 without capturing anything - does not make sense, does it? So there is no missing white piece at g4, so white's last move must have been 0-0-0, so white's king must have been at e1 last move. If that was so, how can black's supposed e-pawn promotion have taken place - exf1=Q# 

 

If the N have not captured anything, then is there any valid logic it went to e3 in front of 2 pawns (it had not given check there), then to f1?


I'm convinced that the solution to this problem will not invoke likelihoods, but rather certainties.  If it's not proveable it's not the solution.

Avatar of WanderingWinder
dsarkar wrote:
WanderingWinder wrote:
dsarkar wrote

N could not have been a promoted piece (white's K was at e1 last move) and at f1 must have captured something there or at e3. total 6 captures accounted for so far.


1st of all, how do you know that white's K was at e1 last move. Furthermore, why did the knight have to capture something on f1 or e3?


white's last move was either 0-0-0 or by the missing piece at g4 - K move from check of immobile B not possible. Now if there is a missing white piece at g4, then neither of the N, B(h2), Q has captured anything - which means black B went to h2 first, then white played g3, then the white B somehow managed to enter to h1, and the black Q followed the white bishop all the time exposed to its attack to g2 without capturing anything - does not make sense, does it? So there is no missing white piece at g4, so white's last move must have been 0-0-0, so white's king must have been at e1 last move. If that was so, how can black's supposed e-pawn promotion have taken place - exf1=Q# 

 

If the N have not captured anything, then is there any valid logic it went to e3 in front of 2 pawns (it had not given check there), then to f1?


You seem to be missing the point; it isn't about finding what moves were played because they were good moves... it's about finding what the possible moves were that led to the position... so hanging pieces is perfectly reasonable. If your only reasoning for theqeen not being allowed to sit on g2 for so long is that white could capture it every move, you have no valid reason in a deductive puzzle whatsoever.

Avatar of dsarkar

I got your point...

yeah, it is a tough one

Avatar of daxelson

The answer is: a black pawn.

It cannot be a white piece, because the bishop on a2 "accounts" for 5 of the six missing white pieces; in order for that bishop to occupy a2, it MUST be the black K-pawn, which reached the second (its seventh) rank, and then captured on b1, promoted to bishop, and moved to a2.

BUT, in order for that to have happened, the K-pawn needed five captures. But the white bishop which started at c1 never moved (blocked in by pawns at b2 and d2).  So the five captured white pieces had to include the K-pawn from e2. 

That accounts for all of the white pieces (five needed to move the black K-pawn to the a-file, plus the black-squared bishop). So the piece on g4 cannot be white.

No other black pawn could have reached the first (its eighth) rank and promoted, since the only other open file is the King (e-)file, and in order to reach that file, more captures would be necessary, and we've already accounted for all the missing white pieces. So with the exception of the a2 bishop, all of the black pieces are "original" pieces. We can see where the "original" black rooks and queen are, so that leaves P, B, or N. We know the g4 piece can't be a black B, or else white could not have castled as his  last move (0-0-0). [White has no other legit last move; his last move HAD to have been castling. So we're down to either black N or black P.

But it can't be a black N, because there have been two captures on the Q-side - pxb3 and something to move the white K-pawn one file to the left. [The white K-pawn was not in position to be captured by the black K-pawn; it had to move to the d-file for that to happen.] But in order to do that, it had to capture either the black N or the black B; it could not have captured a pawn, since all of the black pawns are still present on that side of the board. So in order to account for these two captures, the black N and the black white-squared B must have been captured.

So - the g4 man must be the black g-file pawn.

But I don't see that that answers the "Can black castle?" question

Avatar of dsarkar

Got it!!! This time I KNOW I am correct!

white started with 16 pieces+pawns - he cannot have more than 16!

10 white pieces are on board - therefore 6, and only 6, has been captured!

What happened to the B at c1?? It could not have been captured by the black's promoting pawn (into white-sq B on a2).Therefore it has been captured by some other piece at c1 itself! Therefore neither the N at f1 nor the B at h2 can be a result of pawn promotion, as they needed additional capture (otherwise they could not exist at f1 (from e-pawn) or h2 (from f-pawn)!

Therefore g4 is a black piece/pawn!

g4 cannot be a B or Q as white's last move 0-0-0 would'nt have been possible.

It cannot be a R as already two rooks exist. So g4 must be black N or black P

[edit: it has been proved by daxelson in the post above that g4 is a black pawn].

So if black K and rooks have not moved, black can castle!

Avatar of Georgy_K_Zhukov

I've been seeing a lot of "g4 must be black N or black P! " that. Lets get a single people. You are getting there, but haven't reached it yet!

Avatar of dsarkar

beautiful explanation, daxelson,

white a-pawn captured a piece axb3, and e-pawn captured a piece to the left in order to be in position to be captured by the black pawn! So that is one B and N. That accounts for all black pieces, so g4 is a black pawn! beautiful!

Avatar of _simus_

it's a knight.

reasoning:  most likely not a rook - somewhat because of white's bishop placement suggesting that there was a trade, but more importantly the king placement.  the king would not be where it is because a rook would have had to get there via e1 - checking the king.  if you look at the possible sequences of moves that would resolve the e1 check it just doesn't make sense that that could happen.

 

not even going to mention the bishop....there already is a light squared bishop.

 

not a pawn...structurally impossible.

 

leaving the knight.  checkmate.

Avatar of daxelson
derUbermensch wrote:

I've been seeing a lot of "g4 must be black N or black P! " that. Lets get a single people. You are getting there, but haven't reached it yet!


See my post from 3:11 pm.  I specifically said black pawn - no equivocating - and I explained why it must be a black pawn.

Avatar of TheGrobe

You know, I saw that White's queen-side bishop must have been captured on it's initial square but didn't quite make the leap to deduce that this meant it couldn't have been captured by the pawn that promoted and as a result must be the sixth white piece captured.

Additionally, this means that White's e-pawn must have captured towards the queen-side in order to get into the line of attack of Black's e-pawn that promoted, which means neither it nor the a-pawn captured other pawns.  This means that our two missing pieces, Black's original white-squared bishop and Black's missing knight, must have both been captured by White's pawns and if there must be a piece on g4, it is a Black pawn.  No way around it.

White's last move was clearly O-O-O (and incidentally that the Black Knight came in via h2), but I don't see how it can be determined with any certainty whether Black can or cannot castle.

Nicely done daxelson.

Avatar of dsarkar

Nobody can prove that K and Rs have NOT moved. That means there must be some proof that the K HAS moved...

Avatar of Georgy_K_Zhukov
daxelson wrote:
derUbermensch wrote:

I've been seeing a lot of "g4 must be black N or black P! " that. Lets get a single people. You are getting there, but haven't reached it yet!


See my post from 3:11 pm.  I specifically said black pawn - no equivocating - and I explained why it must be a black pawn.


Sorry to disappoint, but that isn't the answer! There is no way a pawn could be in that position! If you guys want, I'll give a hint or two.

Avatar of David_Spencer

I don't know the answer to the puzzle (working on it), but I think I know why it's not a black pawn. I tried to make a proof game and ran into the problem that if the last move was 0-0-0 and g4 had a black pawn the white h1 Rook was trapped in the corner! Right now the only idea that I have is that White's h and g pawns may have switched places by capturing, liberating the h1 Rook.

Avatar of RyanMK
SirDavid wrote:

I don't know the answer to the puzzle (working on it), but I think I know why it's not a black pawn. I tried to make a proof game and ran into the problem that if the last move was 0-0-0 and g4 had a black pawn the white h1 Rook was trapped in the corner! Right now the only idea that I have is that White's h and g pawns may have switched places by capturing, liberating the h1 Rook.


 If so, that means that black's g and h pawns got traded away...

Avatar of TheGrobe

daxelson's explanation seems pretty bulletproof to me.  I think I need to be convinced why it's not the solution.  There's no question that all six white pieces are accounted for (catptured), and that the two white pawns captured peices, not pawns -- to use daxelson's word, that there is a black pawn on g4 is unequivocal.

Incidentally, white's g and h pawns can't have swapped files becuase if they had, Black's black-squared Bishop could never have arrived on h2.

Avatar of DW_Batty

I have a question: Has is been verified that the bottom of the board is the first rank? The board in the first post doesn't label the ranks and files for me. Specifically, are white's doubled pawns on b2 and b3, or g6 and g7?

Avatar of Georgy_K_Zhukov

The board isn't switched. And Grobe, there is faulty logic there. I'm heading out for a bit to drown my sorrows over Boston's loss, but I'll post a small hint when I return.

Avatar of DW_Batty

Darn, 'cause that would've been a really nice twist. Oh well, I tried, I got nothing now everyone, sorry.

Avatar of TheGrobe

OK -- I see one additional possibility for the presense of Black's black-squared Bishop on h2, which is that it was promoted to a Bishop on g1 after White's g2 pawn had captured something on h2, but before White's h2 pawn had captured something on g2.  This means that there may be three unaccounted for Black pieces as opposed to just two, and that the possibility that it is a Knight on g4 still exists.  Note, again, that it can't be a Bishop because White's last move was O-O-O.

If this is the case, then it must be a Knight on g4 because the pawn can't have captured on the way to promotion (not enough White pieces are missing) so there is clearly no pawn on the g-file, but if not then it must be a pawn based on daxelson's reasoning.

Now, what is wrong with daxelson's reasoning that tells us with certainty that the other Bishop promoted on g1?  I just can't say, but this is a distinct second possibility.

Avatar of TheGrobe

A-ha!

Because White's last move was clearly O-O-O, the King has always been on e1, so the missing White rook, which was captured on the queen-side by the Black pawn that was promoted to a white-squared bishop cannot have gotten out via e1.  This means that the g and h pawns must have swapped ranks in order for the rook to have escaped, and the only way for Black's black-squared bishop to have gotten to h2 in this scenario is if it was promoted to a Bishop on g1.

This means unequivocally, that the piece on g4 is a Black Knight per my reasoning above.

Now, about that castling question....