⑴ Oil drum: the bottom radius is 4 decimeter, the height is 12 decimeter, and the iron sheet area is (40 1.92 square decimeter).
3. The square of14× 4× 2+2× 3.14× 4×12 = 40 1.92 square decimeter.
⑵ Uncovered bucket: the bottom diameter is 40 cm, the height is 50 cm, and the iron sheet area is 7536cm2.
3. 14×(40÷2) squared +3. 14× 40× 50 = 7536 square centimeters.
⑶ Ventilation duct: the section circumference is 0.628m, the height is 1.2m, and the iron sheet area is 0.7536m2.
0.628× 1.2 = 0.7536 m2.
2. The big-headed son wants to give the small-headed father two birthday presents, and the clerk ties the two boxes of gifts into a cross with packaging tape. How long is the packaging tape? (The excess joint is about 20cm) The first rectangle is 40cm long, 30cm wide and 20cm high. The second rectangle is 40 cm long, 30 cm wide and 20 cm high.
(40×2+20×4+30×2+20)×2 = 480 cm.
3. There is a square clearing with a length of 10m. How to design flower beds in open space, so that the area of flower beds accounts for half of the open space?
10× 10 = 100 m2
100 ÷ 2 = 50 square meters
Because there is no description of the shape of the flower bed, the answer is not unique, as long as the area of 50 square meters will meet the requirements.
For the sake of simplicity, I connected the diagonal corners of the square, divided it into two triangles with an area of 50 square meters, and took one of them as a flower bed.