TO RAT :
I think I know the answer now:
(1) 4--4, if level , go to (2),if not goto (5)
(2) 2 balls from step1--2 from the rest 4 ,if level, go to (3),if not goto (4)
(3) 1 from step(2)--one from the rest2 , if not level, this one ,if level , the very last one.
(4) if 2 from the rest 4 is heavier, 1--1 to find the heavier, or if they are lighter ,1--1 to find the lighter.
(5) remove 3 balls from either side ,say the lighter side (sideA)of the unleveled scale ,and put them aside, ; Move 2 balls from the other side(side B) to side A to form a 3-2 distribution, then add one ball from the rest balls to side B , to form a 3--3
(6)if the scale is level now , then we can tell:
a)"the one" is one of the 3 balls removed in step 5
b) "the one" is lighter ( remember we remove 3 balls from the lighter side)
then 1--1 from the 3 balls , if level, the one is the very last, or if not the lighter one
7)if the scale change so that side A become heavier, then "the one" must be heavier and one of the 2 removed from sideB; Weight these 2 balls to find the heavier one .
8)if the scale remain unchanged,we can be sure:
a)of the 6 balls on the scale,3 balls ,one added to sideB and 2 removed from side b in step (5), are sure normal balls.
b)the ditribution of remaining 3 unresolved balls is depend on wether "the one" is heavier or ligher:
if heavier: A:1 normal ball--B:1normal ball+"the one".
if lighter: A: "the one"--B:2 normal balls
so whether "the one" is heavier or lighter can be resolved by weighing the remaining 2 balls on side B to see if they are equal.
If equal , "the one" is the remaining unresolved ball on side A. If not it is the heavier of the 2 unresolved ball on side B.
What a waste!!! |