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If the height of a cylinder is reduced by 2 cm, the surface area will be reduced by 12.56 square cm. What is the bottom area of the cylinder?
First of all, it is clear that height reduction 2 means that the area of the upper and lower circles of the similar cylinder cutting down 2 remains unchanged, so the surface area subtracts the area of the side, that is, the area of the rectangle with width of 2, so the area of the rectangle is 12.56, and the length is the circumference of the upper and lower circles. Let the radius of the upper and lower circles be r, so we can get 2 π R · 2 = 12.56 from the area of the rectangle
From a cylinder with a height of 1 meter and a bottom diameter of 4 decimeters, a small cylinder with a height of 2 decimeters is cut off. How many square minutes has the surface area of the original cylinder been reduced
The reduced area is the side area of the cylinder
The area of the side = the perimeter of the bottom * the height of the small cylinder
Bottom perimeter = pi * 4 = 3.14 * 4 = 12.56 (decimeter)
Side area = 12.56 * 2 = 25.12 (square decimeter)
The surface area of a cylinder is 314 square decimeters, its bottom radius is 5 decimeters, how many decimeters is its height?
What's the bottom area
5 × 5 × 3.14 = 78.5 (square decimeter)
What is the lateral area
314-78.5 × 2 = 157 (square decimeter)
What is the perimeter of the bottom surface
5 × 2 × 3.14 = 31.4 (decimeter)
high
157 △ 31.4 = 5 (decimeter)
The surface area of the cylinder is 56.52 square cm, and the bottom radius is 2cm. What's its height? Fast, let's have a formula/
H is the height; D is the bottom diameter; R is the bottom radius; s is the surface area
S=3.14*d*h
Bring data into equation
56.52=3.14*2*2h
h=4.5cm
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