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A small rectangle is dug out from the middle of a rectangular board with a length of 300cm and a width of 200cm, so that the width around the remaining rectangular frame is the same, and the area of the small rectangle is half of the area of the original board. Calculate the width of the remaining rectangular frame (accurate to 1cm)
Suppose the width of the remaining rectangle is x cm, then the length of the small rectangle is (300-2x) cm, and the width is (200-2x) cm. According to the equation of "the area of the small rectangle is half of the area of the original board": (300-2x) (200-2x) = 300 × 200 △ 24x & sup2; - 1000x + 60000 = 300004x & sup2; - 1000x + 30000 =... "
Saw the biggest circle from a rectangular board 5 decimeters long and 4 decimeters wide. How many square decimeters are the remaining boards?
The area of rectangular board: 5 × 4 = 20 (square decimeter), radius of circle: 4 △ 2 = 2 (decimeter), area of circle: 3.14 × 22 = 12.56 (square decimeter), area of remaining board: 20-12.56 = 7.44 (square decimeter), answer: area of remaining board is 7.44 square decimeter
Saw the biggest circle from a rectangular board 5 decimeters long and 4 decimeters wide. How many square decimeters are the remaining boards?
The area of rectangular board: 5 × 4 = 20 (square decimeter), radius of circle: 4 △ 2 = 2 (decimeter), area of circle: 3.14 × 22 = 12.56 (square decimeter), area of remaining board: 20-12.56 = 7.44 (square decimeter), answer: area of remaining board is 7.44 square decimeter
RELATED INFORMATIONS
- 1. Saw the biggest circle from a rectangular board 5 decimeters long and 4 decimeters wide. How many square decimeters are the remaining boards?
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- 18. In a metal smelter, 27 square ingots of the same size were melted in the furnace and then fired into a rectangular ingot. The length, width and height of the rectangular ingot were measured to be 160cm, 80cm and 40cm respectively. What was the original edge length of the square ingot?
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