A cylinder is a square with a side length of 62.8 cm. What's the surface area of the cylinder?

A cylinder is a square with a side length of 62.8 cm. What's the surface area of the cylinder?

Bottom radius: 62.8 △ 3.14 △ 2 = 10 (CM), surface area: 62.8 × 62.8 + 3.14 × 102 × 2, = 3943.84 + 628, = 4571.84 (square cm); answer: the surface area of this cylinder is 4571.84 square cm

When the side area of a cylinder is expanded, it is a square with a side length of 15.7 cm. What's its radius?

Analysis: after the side of the cylinder is expanded, it is a square, which means that the circumference of the bottom of the cylinder is equal to the height of the cylinder, which is 15.7 cm. That is to say, we know that the circumference of the bottom is 15.7 cm, and we can find its radius. According to C = 2 R, we can find the radius R
5 (CM)
A: its radius is 2.5cm

Calculate the volume of the figure as shown in the figure. (unit: cm)

The volume of cone is: 13 × 3.14 × 42 × 6, = 3.14 × 16 × 2, = 100.48 (cubic centimeter); the volume of cylinder is: 3.14 × (10 △ 2) 2 × 8, = 3.14 × 25 × 8, = 628 (cubic centimeter); answer: the volume of cone is 100.48 cubic centimeter, the volume of cylinder is 628 cubic centimeter