Example: three, three, two, two groups.

1, three and three are symmetrical. If a is light on one side, it is in the light group.

B divide the lamp group into: one, one, one, choose two packages, if they are balanced, the rest is; If it is uneven, the rising bag is.

2, a three and three, if balanced; B is called two and two groups, in the light group; Weigh it again.