1. Divide into 3 parts, choose two piles and weigh them together, which is the light defective product in the pile; If it's as light, that product is in the rest of the pile.

2. Divide into 3 parts, choose two piles to weigh together, and which one is the light defective product in the pile; If it's as light, that product is in the rest of the pile.

3. Divide into three parts and choose two piles to weigh together. Which minor defective product is in the pile; If it's as light, that product is in the rest of the pile.

4. Divide into 3 parts, choose two piles to weigh together, and which one is the light defective product in the pile; If it's as light, that product is in the rest of the pile.