Handwriting for defective products generally adopts the total bracket method, and the format is: T (a, a, a). For example, as follows:

(1) Find the lighter defective products from five table tennis balls. How many times can you weigh them with the scales?

Solution: 5 (2,2, 1) → 2 (1, 1) twice.

5 (1, 1, 1, 1) twice.

(2) One of the nine tennis balls is defective (the defective product is heavier). Can you find it with a balance? It will take at least a few times to find out the defective product. What do you call it?

Solution:

9 (4,4,1) 4 (2,2) 2 (1,1) ... three times.

9 (3,3,3) 3 (1,1,1) ... twice.

9 (2,2,2,2,1) 2 (1,1) ... three times.

9 (1,1,1,1,1,1) ...

We can also find or create other graphic methods to find defective products. In short, the graphic method of finding defective products is not unique. A good method should have the following characteristics: 1 simple and clear, 2 straight images and 3 easy to understand. On the one hand, the graphic method of finding defective products should mobilize the talent of image thinking of primary school students, develop and cultivate students' logical thinking ability, and make them understand the problems in place. On the other hand, whether teachers can use appropriate methods to make students master problem-solving skills easily is a test of teachers' level and a measure of teachers' quality.