put 3 balls on each side, & k- M. B7 v& c& ^
if balance, we can prove that all 6 balls on the 天平 is normal, 5 z1 a9 R W% X" H+ s- G
if not balance, we can prove that the 6 balls outside the 天平 is normal.
) ?1 z/ `& |! V+ kthen use the proved-normal ball on one side and put the other ball on other side W$ b2 ~. [# q4 a4 k6 `
to determine the abnormal is heavy and light |