Split a 20 decimeter long cylindrical wood along the bottom diameter, and increase the surface area by 80 square decimeters. What is the original surface area of this cylindrical wood? (π = 3)

Split a 20 decimeter long cylindrical wood along the bottom diameter, and increase the surface area by 80 square decimeters. What is the original surface area of this cylindrical wood? (π = 3)

The diameter of the bottom surface of the original cylindrical wood is: 80 △ 2 △ 20, = 2 (decimeter); the bottom area of the original cylindrical wood is: 3 × (2 △ 2) 2 = 3 (square decimeter); the side area of the original cylindrical wood is: 3 × 2 × 20 = 120 (square decimeter); the surface area of the original cylindrical wood is: 3 × 2 + 120 = 126 (square decimeter). A: the surface area of the original cylindrical wood is 126 square meters Decimeter

Split a 20 decimeter long cylindrical wood along the bottom diameter, and increase the surface area by 80 square decimeters. What is the original surface area of this cylindrical wood? (π = 3)

The diameter of the bottom surface of the original cylindrical wood is: 80 △ 2 △ 20, = 2 (decimeter); the bottom area of the original cylindrical wood is: 3 × (2 △ 2) 2 = 3 (square decimeter); the side area of the original cylindrical wood is: 3 × 2 × 20 = 120 (square decimeter); the surface area of the original cylindrical wood is: 3 × 2 + 120 = 126 (square decimeter). A: the surface area of the original cylindrical wood is 126 Square decimeter

If three sections of cylindrical wood with a diameter of 20 cm at the bottom are stacked together, if one more section is added, the surface area will increase by 942 m2, and the volume of each section is
What is the volume of each piece of wood?

Only the side area is increased, so the length (height) of each wood is 942 △ 3.14 × 20 = 15cm
The volume of each wood is: 3.14 × (20 / 2) × (20 / 2) × 15 = 4710 cubic centimeter