Saturday, May 28, 2005

VICTORY!!!!!!!!!!!!!!!!!!!!!!!!

Sweet victory... months of agony and mental torture finally comes to an end... if you people are still wondering well Im just talkin about the puzzle involving 12 coins having 1 defective coin ( for details luk at d q... its below this one only)... well ive cracked it... finally!!!!!

alrite here goes the soln
let the 12 coins be divided into 3 groups of 4 coins each such that
group A - A1, A2, A3, A4 COINS
group B - B1, B2, B3, B4 COINS AND SO ON FOR GROUP C

WEIGHING (1)

MEASURE A AGAINST B
1) A = B
WELL THIS ONE IS SIMPLE...
THE WRONG ONE LIES IN GROUP C...
TAKE C1 , C2..
WEIGH AGAINST ANY 2 COINS OF GROUP A AND B ( SINCE THEY ARE ALL NORMAL) { WEIGHING 2}

3 RD WEIGHIN :
IF UNEQUAL THAT MEANS EITHER C1 OR C2 IS DEFECTIVE..... AGAIN WEIGH OF THEM AGAINST 1 NORMAL COIN AND YOULL GET THE DEFECTIVE COIN.....
IF EQUAL THEN DEFCTIVE COIN LIES IN OTHER 2 C COINS IE C3 OR C4... FOLLOW THE SAME PROCEDURE ... WIEGHING AGANIST 1 RIGHT COIN ETC ETC

2) A > B ...( CAN BE THE OTHER WAY ALSO... BUT JUST FOR INSTANCE)....
WELL THIS MEANS C1- C4 ARE ALL NORMAL COINS

WEIGHING (2)
PAN 1 CONSISTS OF - A1 , C1 , C2 , C3
PAN 2 CONSISTS OF - B1 , B2 , A2 , A3

SO WE 'RE LEFT WITH ( THE OTHER POSSIBLE DEFCTIVE COINS) - A4 , B3 , B4

AFTER THIS THERE ARE 3 CASES
A) PAN 1 = PAN 2
THAT MEANS DEFCTIVE IS AMONG A4 , B3 , B4 ... OUT OF WHICH EITHER A4 IS HEAVY OR ONE OF B3 AND B4 IS LIGHT SINCE WE ALREADY KNOW ( BY 1 WEIGHING ) THAT A > B

SO 3RD WEIGHING WILL BE AS FOLLOWS...
PAN 1 - A4 , B3
PAN 2 - C1, C2 ( IE ANY OF THE NORMAL ONES)
AGAIN 3 POSSIBLITIES,,,,
1) PAN 1 = PAN 2..
SO A4 AND B3 ARE NORMAL... IE B4 IS DEFCTIVE

2) PAN 1 > PAN 2
SINCE WE KNOW THAT OUT OF A4 AND B3 ... A4 CAN POSSIBLY BE THE HEAVY ONE ( AS BELONGS TO A... WHICH WAS HEAVIER)... HENCE A4 IS THE DEFECTIVE COIN

3) PAN 1 < PAN 2...
JUST LIKE THE ABOVE CASE,,,, THIS TIME THE DEFECTIVE COIN WOULD BE B3 ( BELONGS TO B GROUP.. WHICH WAS LIGHTER ETC).......

NOW GOING BACK TO THE INTIAL PAN 1 AND PAN 2
IF PAN 1 NOT EQUAL TO PAN 2
IE DEFECTIVE COIN IS AMONG A1 , B1 , B2 , A2 , A3

B) PAN 1 > PAN 2
SINCE THIS IS THE PREV RECORDING ONLY ( FOR A > B)... THIS MEANS MOVING A2 AND A3 TO THE OTHER SIDE HAD NO EFFECT ... THE DEFECTIVE COIN REMAINS IN ITS ORIGINAL POSITION... SO IT HAS TO BE AMONG A1 , B1 , B2 OUT OF WHICH WE KNOW ( THROUGH WEIGHIN 2 ) THAT EITHER A1 IS HEAVY OR ONE OF B1 AND B2 IS LIGHT AS PAN 1 > PAN 2..
NOW THE DEFTIVE COIN CAN BE OBTAINED BY THE SAME PROCEDURE AS MENTIONED BEFORE ( FOR PAN 1 = PAN 2)

C) PAN 1 < PAN 2
THIS MEANS MOVING A2 AND A3 BROUGHT ABOUT A CHANGE IN THE POSITION OF THE DEFCTIVE COIN SO THE DEFCTIVE IS EITHER A2 OR A3.... WEIGH ANY OF THEM AGAINST A NORMAL ONE ... IF EQUAL THEN THE OTHER ONE IS THE DEFECTIVE COIN ( THE DEFECTIVE COIN WOULD BE HEAVIER PLS NOTE AS PAN 2 > PAN 1) IF NOT EQUAL THEN OBVIOUSLY THAT VERY COIN IS DEFECTIVE

SO I HOPE THE SOLUTION IS FULL PROOF ... ANY QUERIES OR LOOPHOLES PLS DO COMMENT

4 Comments:

Blogger AJ said...

I'm sure this blog has never seen such a long entry!
I hope someone can figure out its essense!

3:32 PM  
Blogger Dhruv Raj said...

uh...yaa...this is the problem or the solution??

10:52 AM  
Blogger Quizolk said...

just happened to run across this blog.
If the problem it to find the defective coin ONLY, then your solution is full. But I think the original question is to find the defective coin AND say whether it is heavier or lighter than the rest. In this case, your solution is almost complete, failing only when the first three weighing is equal, in which case the last unweighed coin is unknown whether it is lighter of heavier than the rest. Cheers!

10:27 AM  
Anonymous Anonymous said...

The solution is incomplete as yet to find out light or heavy.....
there is a much simpler solution....

12:22 AM  

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