6.28 decimeter < 15.7 decimeter
4dm=4dm
This iron can be made into a chimney.
5. The topic is cylindrical oil drum, so its area is side area +2 bottom area. And there are five questions to do, and finally multiply them by five to get the answer. The process is as follows:
The height of the oil drum is 24÷2= 12cm.
1 oil drum area π×(24÷2)? × 2+(π× 24 )×12 =1808.64 (square centimeter)
The area of five oil drums is 1808.64×5=9043.2 (square decimeter).
A: It needs at least 9043.2 square decimeters of iron sheet.
6. This problem is equivalent to calculating the side area of this cylinder, plus the area of a round bottom (because there is no cover). The process is as follows:
Transverse area 4 x 5 = 20 (square decimeter)
Bottom area ωω(4/2)? = 12.56 (square decimeter)-π is 3. 14 with a radius of 2dm.
The total area is 20+ 12.56=32.56 (square decimeter).
A: At least 32.56 square decimeters of iron sheet is needed.
π in the above question is 3. 14. I'm only a junior two student, so it's not easy to help you answer questions and type. I hope it can be adopted and praised.