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The process of exercise 8.3 4 5 6 7 8 9 in the second volume of the seventh grade mathematics textbook
Solution: the box body is made of X pieces of iron sheet and the bottom of the box is made of Y pieces of iron sheet, which can make the box body and the bottom of the box just match.

X+y=36。

25×2x=40y

The solution is x= 16.

y=20

5. Solution: A cart and a car can transport X tons and Y tons respectively at one time.

2x+3y= 15.5。

5x+6y=35

The solution is x=4.

y=2.5

So 4×3+2.5×5=24.5 (ton)

6. solution: let the uphill distance from a to b be x km and the flat road distance be y km.

Then x+ y= 54/60.

5 x+ 4 y= 24/60。

The solution is x= two thirds.

Y= eight fifths

7. Solution: Suppose that X kilograms of disinfectant containing 30% drugs and Y kilograms of disinfectant containing 75% drugs are needed.

X+y= 18。

30%x+75%y= 18×50%

The solution is x= 10.

y=8

8. Solution: We assume that before the discount, each commodity of commodity A is X yuan, and each commodity of commodity B is Y yuan. According to the meaning of the question, you will get.

60x+30y= 1080

50x+ 10y=840

The solution is x= 16.

y=4

A: It's cheaper than no discount, 400 yuan.

9. Solution: X yuan for each toothbrush and Y yuan for each box of toothpaste.

39x+2 1y=396

52x+28y=5 18

The system of equations has no solution, so this record is wrong.

It must be correct, the textbook is completely solved! ! !

Despise sneak attack! !

References:

Complete solution of teaching materials

Comment | 1

Report |20 10-04-23 12:39 Waiting for the lonely snow in spring | Level 1

4. Solution: The box body is made of X pieces of iron and the bottom of the box is made of Y pieces of iron, which can make the box body and the bottom of the box just match.

X+y=36。

25×2x=40y

The solution is x= 16.

y=20

5. Solution: A cart and a car can transport X tons and Y tons respectively at one time.

2x+3y= 15.5。

5x+6y=35

The solution is x=4.

y=2.5

So 4×3+2.5×5=24.5 (ton)

6. solution: let the uphill distance from a to b be x km and the flat road distance be y km.

Then x+ y= 54/60.

5 x+ 4 y= 24/60。

The solution is x= two thirds.

Y= eight fifths

7. Solution: Suppose that X kilograms of disinfectant containing 30% drugs and Y kilograms of disinfectant containing 75% drugs are needed.

X+y= 18。

30%x+75%y= 18×50%

The solution is x= 10.

y=8

8. Solution: We assume that before the discount, each commodity of commodity A is X yuan, and each commodity of commodity B is Y yuan. According to the meaning of the question, you will get.

60x+30y= 1080

50x+ 10y=840

The solution is x= 16.

y=4

A: It's cheaper than no discount, 400 yuan.

9. Solution: X yuan for each toothbrush and Y yuan for each box of toothpaste.

39x+2 1y=396

52x+28y=5 18