Re: puzzles, coin weighing, coding, 15 COINS.

> From: Van Vu <t-vanvu@microsoft.com>
> Hi ca?  lang,
> ------------------------------------------------------------------------
> ------------------------------------------------------------------------
> ------
> About 12 -13 coins problem: You can certainly find the bad coin among 13
> as follows:
> 
> partition 4-4-5. weight 4 with 4 , if not equal than the bad coin is
> here and process as in the 12 coins case. 
> 
> if equal than the bad coin is in the last 5. Take 3 of them and weigh
> with 3 good coins (all coins
> from the first weighing are good). If non equal than you know that the
> bad coin is among 3 
> and also know if it is lighter or heavier. Than finish as usual.  If the
> 3-3 weighing is equal than the bad coin is in the last 2. Take any of
> them and weigh with a good coin and you are done.
> 
> I guess one cannot find the bad coin among 14, using 3 weighing. Can you
> prove that ?
> ------

Sorry ca'c ba'c, ho^m qua tui ngoi la^u tren truong ne^n me^.t va` viet
nha^`m 15 coins tha`nh 13 coins. De^~ hieu la` khi puzzle of 12 coins co'
lo+`i giai thi` 13 coins cu~ng co'. 

Khi bo.n to^i ddo^' nhau ba`i 112 coins, to^i co' anh ba.n chi? ra ca'ch
so sa'nh 5-5 o+? ngay la^`n dda^`u, neu le^.ch ca^n ha('n va^~n ti`m ra
lo+`i gia?i !?, => bai` to'an co' lo+`i gia?i cho ca? truong ho+.p 15
coins !! Nhu+ng to^i k0 nho+' ha('n ca^n nhu+ the^' na`o vi` qua' la^u
roi. 

Ba'c na`o co' y' gi` hay khi so sa'nh 5-5 ?

best,

    ,    ,
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                                                Vu~ Quo^'c Hu`ng
						hung@vsb.cz.
+---------------------------+----------------------------------------+
     "Bill Gate's daughter will be the best product from MS".