There are two ways to encircle a cylinder with a rectangular sheet of iron 31.4 decimeters long and 12.56 decimeters wide. One is () decimeters in diameter and () decimeters in height. The other is () decimeters in diameter and () decimeters in height

There are two ways to encircle a cylinder with a rectangular sheet of iron 31.4 decimeters long and 12.56 decimeters wide. One is () decimeters in diameter and () decimeters in height. The other is () decimeters in diameter and () decimeters in height

There are two ways to encircle a cylinder with a rectangular sheet of iron 31.4 decimeters long and 12.56 decimeters wide. One is (10) decimeters in diameter and (12.56) decimeters in height. The other is (4) decimeters in diameter and (31.4) decimeters in height

After cutting off a 2-meter-long cylinder, the original surface area will be reduced by 12.56 square decimeters. What is the original surface area?
After cutting off a 2-meter-long cylinder, the original surface area will be reduced by 12.56 square decimeters. How many square decimeters is the original surface area?

The reduced surface is the side area of a cylinder of 2 decimeters, which is equal to the circumference of the cylinder multiplied by the height of the cylinder
That is: D * 3.14 * 2 = 12.56
If d = 2, r = 1 decimeter
So the original surface area s = 1 * 1 * 3.14 * 2 + 2 * 3.14 * 20 = 131.88 square decimeters

There is a 12.56 decimeter long cylinder of the machine, its side is just a square, find the surface area of the machine

The length of the cylinder is 12.56 decimeters, which means that its height is 12.56 decimeters, and its expansion is a square. In other words, the height of the cylinder is exactly the side length and the circumference of the bottom surface of the square. The area of the square + the area of the two bottom surfaces = the surface area of the cylinder,
So we use 12.56 × 12.56 = 157.7536 to get the square area,
The radius is 12.56 △ 3.14 △ 2 = 2, that is, the area of two bottom surfaces is 3.14 × 2 & # 178; × 2 = 25.12
Surface area = 157.7536 + 25.12 = 182.8736