Mathematics diary of grade 6 of primary school (Volume 2)

Mathematics diary of grade 6 of primary school (Volume 2)

Today, I went to Xinhua Bookstore to read a mathematics book. I learned what a cylinder is and its side area and surface area. I understood and mastered the calculation formulas of the side area and surface area of a cylinder, and I was able to use these formulas to calculate their side area and surface area to solve practical problems
First of all, I would like to talk about the understanding of the cylinder: we often see tea cans, cans, pen barrels, lamps, round steel in our daily life The shape of these objects are all cylinders. The upper and lower surfaces of a cylinder are called the bottom surfaces. They are two identical circles. The distance between the two bottom surfaces of a cylinder is called the height. From the upper bottom to the lower bottom of a cylinder, countless heights can be drawn
Secondly, the understanding of the cylinder area: expand the side of the cylinder, you can get a rectangle, the area of the rectangle is the side area of the cylinder. How to calculate the side area of the cylinder? If s is the side area of the cylinder, C is the perimeter of the bottom, H is the height, the calculation formula of the side area of the cylinder can be written as: S = ch
The sum of the side area and the two bottom areas of the cylinder is the surface area of the cylinder. The surface area of the cylinder = the side area + the two bottom areas
The bottom radius of a cylinder is 20 cm and its height is 44 cm. How many square centimeters is its surface area?
(1) What is the side area of the cylinder in square centimeters?
S=2πrh=2XπX20X44=1760π
(2) What's the floor area in square centimeters?
S=πxrxr=πx20x20=400π
(3) What is the surface area of the cylinder in square centimeters?
1760 π + 400 π x2 = 2560 π = 8038.4 (cm2)
A: the surface area of this cylinder is 8038.4 square centimeters