im sorry, but actually i dont quite get this bit. so if lets say
C4 is not the counterfeit, are you gonna remove anything from the
scale first before your next step?
you remove C2, and you put either C1 or C2 on the LHS am i
right? and on the other side you have 2 coins. but its already not
balanced when its a 1v2 right?
actually 1 more question i have to ask is whether removing of
coins counts as a try.
In my 1st try, I eliminated group A and B.
Before my 2nd try I know the counterfeit is in group C.
Either C1, C2, C3 or C4.
C4 is removed BEFORE try no.2.
Try No.2 consist of C1, C2, C3 AND 1 GENUINE coin from the 8
genuine coins I discovered in try No.1
I put C1+C3 on the left hand side AND C2 WITH the genuine coin
on the RHS.
If C1+C3 balanced with C2+genuine coin, then C4 is the
counterfeit.
Now if they don't balance, the counterfeit is either C1,C2 or
C3.
PRETEND C1+C3 was heavier than C2+genuine on the 2ND TRY.
Now I remove C3 from the weighting and move C2 to the LHS. Put 2
geniune coins on the RHS.
NOW I have C1+C2 on the LHS and 2 geniune coins on the RHS.
PRETEND C1+C2 is lighter than the 2 genuine coins. THIS MEAN LHS
was heavier on the 2nd try BUT lighter on the 3rd try. Since the
scale tilt, IT MUST BE because the counterfeit SWITCHED sides.
Since C2 switched sides, C2 is the counterfeit.
Since C1(geniune)+C2(counterfeit) is lighter than 2 genuine
coins, thus counterfeit is lighter.
I illustrated 1 situation to you. You can test the other
situations.