For a cylinder, the height is 4 decimeters, and the bottom radius is 2.4 decimeters?

For a cylinder, the height is 4 decimeters, and the bottom radius is 2.4 decimeters?

Cut a cylinder with a bottom diameter of 12 cm along the diameter to get two cylinders. At this time, the surface area of the two half cylinders increases by 120 square centimeters compared with the original cylinder. What is the surface area of this cylinder?

120 / 2 = 60, 60 / 12 = 5cm, so the height of the column is 5cm, the area of the upper and lower bottom is 3.14 * 6 * 6 * 2 = 226.08 square cm, the side area is 2 * 3.14 * 6 * 5 = 188.4 square cm, so the surface area of the column is 226.08 + 188.4 = 414.48 square cm

The lower cylinder is cut vertically along the direction of the arrow, and the surface area is increased by 40 square centimeters

According to the stem analysis, the height of the cylinder: 40 △ 2 △ 4 = 5 (CM), so the surface area is: 3.14 × (42) 2 × 2 + 3.14 × 4 × 5, = 25.12 + 62.8, = 87.92 (square cm). A: the surface area of the cylinder is 87.92 square cm

The surface area of a cylinder can be calculated by the formula: 2 π R * (R + H)?

That's right
By deforming the surface area of the cylinder, we can get
Surface area of cylinder = bottom area × 2 + side area
=2πrr+2πrh
=2πr(r+h)

If the height of a cylinder is reduced by 2 cm, its surface area will be reduced by 25.12 square cm. What is the bottom area of the cylinder______ Square centimeter, reduced volume______ Cubic centimeter

25.12 △ 2 = 12.56 (CM), 12.56 △ 3.14 △ 2, = 4 △ 2, = 2 (CM), 3.14 × 22 = 12.56 (square cm), 12.56 × 2 = 25.12 (cubic cm); answer: the bottom area of this cylinder is 12.56 square cm, the volume is reduced by 25.12 cubic cm. So the answer is: 12.56, 25.12

Is it right to divide a cylinder into two small cylinders equally, and the surface area of each small cylinder is half of the original surface area?
Is it right or wrong that the volume of a cylinder is two-thirds larger than that of a cone with the same base and height?

Wrong! Because after a cylinder is divided into two, the bottom area of the cylinder will not change, but the side area of each small cylinder will become half of the original! So the surface area should be greater than half of the original cylinder surface area!
You can ask questions if you don't understand,

A cylinder is divided into two small cylinders averagely. The surface area of the small cylinder is 12______ (judge right or wrong)

A cylinder is divided into two small cylinders equally. The surface area of each small cylinder is half of that of the large cylinder plus the bottom area of one cylinder

Cut a cylinder into two small cylinders averagely. The surface area of each small cylinder is half of the original. Right or wrong

It's wrong
After cutting, the bottom area of the cylinder does not change, but the side area becomes half of the original
So the surface area after cutting = 2 * bottom area + 1 / 2 of the side area of the original cylinder, and the original surface area = 2 * bottom area + the side area of the original cylinder
So the surface area of each small cylinder is not equal to half of the original

Cut a cylinder into two small cylinders. The surface area of a small cylinder is 12______ ．

The side area of the small cylinder after cutting is half of the side area of the original cylinder, and the bottom area of the small cylinder is equal to the bottom area of the original cylinder, so the surface area of the small cylinder is not half of the surface area of the original cylinder

The volume of a cylinder is 452.16 cubic centimeters, and the height is 4 centimeters. Find the surface area of the cylinder

The surface area of the cylinder can be obtained by calculating the bottom area from the volume and height, and then the radius, 3.14 * diameter * height + 2 bottom area
Bottom area = 452.16 △ 4 = 113.04
Bottom radius square = 113.04 △ 3.14 = 36 = 6 × 6
Bottom radius = 6
Bottom diameter = 6 × 2 = 12
Perimeter of bottom surface = 12 × 3.14 = 37.68
Side area = 37.68 × 4 = 150.72
Surface area = 150.72 + 113.04 × 2 = 376.8 square centimeter