"Equivalence relation" refers to the equal relation between quantities, which is one of the quantitative relations. Mathematical problems often contain many equivalence relations. For example, if we use equations to solve practical problems, we must find out the equivalence relationship in the problems.

conventional process

1, grasping key mathematical terms to find equivalence relation.

Quantitative relationship in practical problems: general sum-difference relationship or multiple relationship, which is often expressed by terms such as "one * * * has", "greater than ……", "less than …" and "several times more than ……". When solving problems, you can find the equivalence relation by grasping these terms, and list the equations in narrative order.

2. Find the equivalence relation according to the common quantitative relation.

Common quantitative relationship: working efficiency × working time = total workload; Unit price × quantity = total price; Speed × time = distance and so on.

3. Find out the equivalence relation according to the commonly used calculation formulas.

The commonly used calculation formula is the area formula of geometric figures: rectangular area = length × width; Triangle area = 1/2 (base × height); Parallelogram area = base × height.

4. Draw a line segment and find out the equivalence relation.

For example, "a farm has 400 hectares of wheat, and 70 hectares of wheat are harvested every day for the first three days, and the rest are harvested in two days." How many hectares of wheat will be harvested on average every day? " Draw a line diagram according to the meaning of the question first. It can be seen intuitively from the line chart that the total wheat harvest = the wheat harvest in the first three days+the wheat harvest in the last two days. According to this relationship, the equation 70× 3+2x = 400 can be listed.