1. Aunt Wang made a cylindrical pillow with a length of 80 cm and a base diameter of 18 cm. If the side is printed cloth and the bottom is yellow cloth, how much does each cloth cost?

solve

Bottom circumference =18× 3.14 = 56.52cm.

Bottom area =18 ÷ 2×18 ÷ 2× 3.14 = 254.34 (square centimeter).

Canvas area = bottom circumference × pillow length =56.52×254.34=452 1.6 (square centimeter)

Yellow cloth area = bottom area ×2=254.34×2=576 (square centimeter)

Answer: The edge cloth is 45,265,438+0.6 square centimeters; The bottom is made of 576 square centimeters of yellow cloth.

2. The width of satellite TV paper is 10 cm, and the diameter of the middle cardboard shaft is 3.5 cm. How much cardboard does it take to make the intermediate shaft?

solve

Paper axis circumference =3.5×3. 14= 10.99 (cm)

3.5× 3.14×10 =109.9 (square centimeter)

Answer: The central axis needs cardboard with a length of 10.99 cm and a width of 10 cm. The area of this cardboard is 109.9 cm 2.

Xiaomi made a cylindrical lantern. There are 78.5 square centimeters between the upper and lower bottom surfaces. How much colored paper did he use?

Lack of known conditions

4. Cylindrical iron drum (without cover), with a height of 12DM and a bottom diameter of 3/4 of the height. How much iron does it take to make this barrel?

solve

Bottom diameter = 12×3/4=9 (decimeter)

Bottom circumference =9×3. 14=28.26 (decimeter)

Bottom area =9÷2×9÷2×3. 14=63.585 (square decimeter)

Transverse area of bucket = 12×28.26=339. 12 (square decimeter)

The required iron sheet =339. 12+63.585=402.705 (square decimeter)

A: It takes about 402.705 square decimeters of iron to make this barrel.