The following is a rectangular cardboard, cut the shadow part according to the figure, just can make a cylinder. Calculate the surface area of the cylinder Don't use π solution, don't use equation, seek explanation. It doesn't matter if the formula is longer

The following is a rectangular cardboard, cut the shadow part according to the figure, just can make a cylinder. Calculate the surface area of the cylinder Don't use π solution, don't use equation, seek explanation. It doesn't matter if the formula is longer

41.12 / (3.14 + 1 + 1) = 8, which is the diameter and the height
3.14x（8/2）²x2+（41.12-8-8）x8=301.44

The following is a rectangular cardboard, according to the diagram cut the shadow part, just can make a cylinder!
No equations, please explain. Thank you

You have an important information that you haven't mentioned, that is, the circle should be tangent to both the edge of the small rectangle and the edge of the large rectangle. Then you can solve this problem. The first method: the first step: first, find out the radius of the two circles: 41.12 / (4 + 2 π) = 4. Why? Because you want to form a cylinder, the small rectangle

Cut the shadow part of a rectangular cardboard as shown in the figure, just to make a cylinder, calculate the surface area and volume of the cylinder (to solve the problem and process)

Because the rectangle in the figure can be enclosed into a complete cylinder, the length of the rectangle is equal to the circumference of the circle. The diameter of the circle is 18.84 △ 3.14 = 6 (DM). When the diameter of the circle is known, the height of the cylinder is 10cm minus the diameter of the circle: 10-6 = 4 (DM). When the diameter and height of the circle are known, the surface area can be calculated