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        riddles >> easy >> What Move MUST Black Have Played?
        
(Message started by: THUDandBLUNDER on Sep 7^th, 2003, 10:00pm)

Title: What Move MUST Black Have Played?
Post by THUDandBLUNDER on Sep 7^th, 2003, 10:00pm

It is Black to move.

Find one move he must have played during the game in order to arrive at the position below.

Title: Re: What Move MUST Black Have Played?
Post by BNC on Sep 7^th, 2003, 11:10pm

Just one move? OK.
Sorry for not using the standard notations...

[hide]Black knight G3 -> H1[/hide]

Now, I'm not much of a chess player, so this is either wrong, or just too easy.... probably wrong.

Title: Re: What Move MUST Black Have Played?
Post by THUDandBLUNDER on Sep 8^th, 2003, 12:32am

Yeah, the most obvious answer of N (on g3) takes R (on h1) is not correct.

In fact, it can be proved that this did not happen.

Title: Re: What Move MUST Black Have Played?
Post by BNC on Sep 8^th, 2003, 3:04am

OK, how about this (again, sorry for not using proper notations):

1. W: NG1 -> H3; B: NB8 -> C6
2. W: RH1 -> G1; B: NC6 -> D4
3. W: NB1 -> A3; B: ND4 -> F3
4. W: NA3 -> B1; B: NF3 -> G1 (takes R)
5. W: NB1 -> A3; B: NG1 -> F3
6. W: NA3 -> B1; B: NF3 -> D4
7. W: NB1 -> A3; B: ND4 -> C6
8. W: NA3 -> B1; B: NC6 -> B8
9. W: NH3 -> G1

And it’s black’s turn.

Is it legal? (note that the white moves may be adjusted somewhat)

If so, the move would be black night F3->G1

Title: Re: What Move MUST Black Have Played?
Post by THUDandBLUNDER on Sep 8^th, 2003, 4:23am

Quote:

3. W: NB1 -> A3; B: ND4 -> F3

Sorry, after ND4 -> F3 the White king is in check.

Title: Re: What Move MUST Black Have Played?
Post by wowbagger on Sep 8^th, 2003, 5:15am

An "easy" one again, huh? ;)

on 09/08/03 at 00:32:22, THUDandBLUNDER wrote:

Yeah, the most obvious answer of N (on g3) takes R (on h1) is not correct.

In fact, it can be proved that this did not happen.

How about this reasoning to show that the White Rook cannot have been captured on h1:
[hide]Black must have made an even number of moves with his Knight(s) (other pieces disallowed by final position). If he captures the Rook on h1, White has to make all his moves with his Knight(s), too. Thus, it would be White's turn, not Black's[/hide].
Therefore, the White Rook was captured on g1. Thinking a bit further, we find that [hide]the Black Knight has two possibilities: Nf3xg1 or Nh3xg1. As T&B has already pointed out, in the first case Black would have checked the White King, so this is ruled out. Hence, Kh3xg1 is the move Black must have played[/hide].

Title: Re: What Move MUST Black Have Played?
Post by THUDandBLUNDER on Sep 8^th, 2003, 6:13am

Quote:

(other pieces disallowed by final position)

Well, he could have moved his rooks (an even number of times).

Quote:

If he captures the Rook on h1, White has to make all his moves with his Knight(s), too.

Likewise for White.

Quote:

Hence, Kh3xg1 is the move Black must have played.

Of course, here you mean Nh3xg1. :)

Well done, wowbagger. I think you are getting the hang of these now.

Title: Re: What Move MUST Black Have Played?
Post by wowbagger on Sep 8^th, 2003, 6:51am

on 09/08/03 at 06:13:41, THUDandBLUNDER wrote:

Well, he could have moved his rooks (an even number of times).
Likewise for White.

Right. Good for me that this doesn't change the basic argument.

Quote:

Of course, here you mean Nh3xg1. :)

You're right again. Sorry to anyone who got confused.

Quote:

Well done, wowbagger. I think you are getting the hang of these now.

At least of the easy ones. ;)
Good to know I haven't completely wasted all my time today. :D

Title: Re: What Move MUST Black Have Played?
Post by Seva Gunitskiy on Sep 8^th, 2003, 11:16am

Assuming these are both terrible chess players, why not:

1. g1-f3; g8-f6
2. f3-g1; f6-e4
3. g1-f3; e4-g3
4. f3-g1; g3Xh1

black knight then retraces its steps back to g8

Title: Re: What Move MUST Black Have Played?
Post by THUDandBLUNDER on Sep 8^th, 2003, 11:24am

Quote:

black knight then retraces its steps back to g8

OK, try. Don't forget we need the original puzzle position with Black to move.