How to find equal relationship? detailed

1, master 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.

For example, "the school has carried out tree planting activities, and planted 50 trees in the fifth grade, four fewer than in the fourth grade." How many trees were planted in the fourth grade? " The key word of this question is "less than …", from which we can find the equivalence relation: 2 times the number of trees planted in the fourth grade minus 4 equals the number of trees planted in the fifth grade, thus listing the equation 2-4 = 50.

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 ... When solving problems, we can find equivalence relations according to these quantitative relations.

For example: "The retail price of a certain style of clothes is 36 yuan 1 set, and the current price is 2 16 yuan. A * * *, how many sets of clothes can I buy? " According to the quantitative relationship of "unit price × quantity = total price", equation 36 = 2 16 can be listed.

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

Commonly used formulas are: rectangular area = length × width; The equivalence relation can be found according to the calculation formula. For example, "the area of a rectangle is 19 square meter, its length is 4 meters, so how many meters is its width?" According to the formula "length× width = area", Equation 4 = 19 can be listed.

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

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.

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? "

Extended data:

Common equivalence relation:

1, subtraction equivalence relation

Negative = negative+difference

Difference = minuend-minuend

Subtraction = minuend-difference

2. Addition equivalence relation

Appendix = Sum-Another Addendum

Sum = Appendix+Appendix

3. Multiplication equivalence relation

Product = factor × factor

Factor = product ÷ another factor