2. If they can't be shared equally, they will also make a difference between one more and one less 1.

3. Method: Three pieces (or three piles) of articles are randomly weighed once, and the balance: the defective products are under the balance; Unbalance: defective products are found on the balance (according to the weight or lightness given in the title).

4. Know the weighing time and find out the number of items: 3n.

5. Know the number of items and find the weighing times: take the value of n, 3n- 1

6. If the weight is unknown, mark weight 1, weight 2, weight 3, ... weight 1, weight 2, weight 3 ... after each weighing. Compared with the weighing balance, the abnormality is defective.