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The key of solving practical problems by quadratic equation of one variable is
Find the same relationship!
Uncle Li chose 15 kilograms of broad beans and 35 kilograms of vegetables to sell in the market, and got 78 yuan in total. The price of a kilogram of broad beans is twice that of a kilogram of vegetables. How much do you get for each of them?
Set a kilogram of vegetables X Yuan, then a kilogram of broad beans 2x yuan
35X+15*2X=78
X=78/65
35X=42
15*2X=36
A: Uncle Li gets 36 yuan for broad beans and 42 yuan for vegetables
Use equations to solve practical problems
(1) a piece of iron wire can be enclosed into a square with a side length of 15 cm. If it is enclosed into an isosceles triangle with a bottom of 12 cm, how long is the waist of the isosceles triangle?
(2) in the experimental primary school, there are 8 boys less than 4 times of the girls and 24 more than 3 times of the girls in the math interest group. How many boys and girls are there in the math interest group?
First question
Set waist length X
2X+12=15X4
2X=48
X=24
Second question
Set girls as X people
4X-8=3X+24
4X=3X+32
X=32
32X4-8=120
A: 32 girls and 120 boys
Adopt Oh Pro
The key of using equation to solve practical problems is ()
A. Solve equation B. set unknown number C. find equivalent relation D. set equation
The main steps of solving practical problems by listing binary linear equations are as follows: (1) according to the problem, set the unknowns, which are generally represented by X and Y; (2) according to the unknowns, determine the equality relationship in the problem, and list the equations. Generally, if you select several unknowns, you need to list several equations. If you select two unknowns, you need to list the equations according to the equality of the problem List two equations (3) to solve the equations composed of these equations, find out the value of the unknowns, and determine the solution of the problem according to the practical significance of the problem. The key in the above steps is to find the equivalent relationship, so choose C
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