For any application problem, you can write a basic quantitative relationship according to the conditions and problems, which is the equivalence relationship in the problem.

For example, "There used to be some jiaozi powder in the store, but it was delivered 12 bags each weighing 5 kg. After selling 7 bags, there are still 40 Jin left. How many kilograms of jiaozi powder does this shop have? " According to the narrative order of the topic, we can easily write: original weight+delivered weight-sold weight = remaining weight.

2. Closely follow the formulas of perimeter, area and volume of geometric shapes to determine the equivalence relation.

When studying geometry, students have mastered the formulas for calculating the perimeter and area of plane graphics and the surface area and volume of three-dimensional graphics. These formulas are the embodiment of equivalence relation.

For example, "The area of a triangle is 100 square centimeter, the base is 25 centimeters, and the height is how many centimeters?" We can directly list the equations according to the triangle area calculation formula.

3. Determine the equivalence relation according to the common quantitative relation.

Grade three students have learned the common quantitative relations in multiplication and division application problems. For example, unit price × quantity = total price, single output × quantity = total output, speed × time = distance, work efficiency × time = total work, etc. These common basic quantitative relations are equivalent relations.

4. Grasp the key sentences and determine the equivalence relationship.

Many application problems have sentences that reflect the quantitative relationship. When solving problems, as long as we find this key sentence and correctly understand its meaning, we can determine the equivalence relationship.

For example, according to "the number of choirs is 3 times more than that of dance teams, 15", we can know that the number of dance teams × 3+ 15 = the number of choirs. According to "there are 180 peach trees and apricot trees in the orchard", we can know that the number of peach trees+apricot trees = 180.

5. Determine the equivalence relation with the help of line segment diagram.

The line graph can concretize the abstract quantitative relationship and make the hidden quantitative relationship clear. For more complicated topics, students can find the equivalent relationship with the help of line segment diagrams.

For example, "There are two bags of rice, and the weight of bag A is 1.2 times that of bag B. If you put another 5 kilograms of rice in bag B, the two bags will be equally heavy. How many kilograms are there in two bags of rice? "