1. In the multiplication formula, if one factor is a constant and another factor is multiplied (or divided) by a number (except 0), the product will also be multiplied (or divided) by this number. For example: 4X6=24, 4x 12=48, 2x6= 12.
2. In the multiplication formula, one factor multiplies (or divides) a number (except 0) and the other factor divides (or multiplies) the same number, and the product of the two remains unchanged. For example: 9x 12= 108, 18x6= 108, 3x36= 108.
3. In the multiplication formula, one factor A is multiplied by m, another factor B is multiplied by n, and the product C is multiplied by m and then multiplied by n, (m≠0, n≠0). For example: 2x3=6, 6x 12=72.
4. In the multiplication formula, one factor A is multiplied by m, another factor B is divided by n, and the product C is multiplied by m and then divided by n, (m≠0, n≠0). For example: 6x 8 = 48 12 x2 = 24.
5. In the multiplication formula, one factor A is divided by m, another factor B is multiplied by n, and the product C is divided by m and then multiplied by n, (m≠0, n≠0). For example: 27x4= 108, 9x8=72.
6. In the multiplication formula, one factor A is divided by m, another factor B is divided by n, and the product C is divided by m and then divided by n, (m≠0, n≠0). For example: 64x9=576, 8x3=24.
Extended data:
The teaching content of this lesson is Example 4 of Unit 3, Volume 1, Grade 4-"The Changing Law of Product". Exploring the changing law of product in multiplication operation is an important aspect of the content structure of integer four operations. Taking two sets of multiplication formulas as the carrier, the textbook examples guide students to explore the change of the product of one factor when the other factor is unchanged, and summarize the changing law of the product.
In the process of this exploration, I let students understand that when two numbers are multiplied, the product changes with the change of one factor (or two factors), and at the same time realize that things are closely related and are inspired by dialectical thinking.