1. There are eight identical columns in a pavilion in the forest park, with a height of 3 meters and a base diameter of 40 cm. Now paint all these columns. What is the area of the paint part?

0.4 * 3.14 * 3 * 8 = 30.144 m2

2. Build a cylindrical pool with a bottom diameter of 4m and a depth of 3m. The inner wall and bottom of the pool are coated with cement. What is the area of plastering part?

2 * 2 * 3.14+4 * 3.14 * 3 = 50.24 square meters

3. The side area of the cylinder is 9.42 square centimeters, and the bottom diameter is 3 centimeters. What is the height of this cylinder?

9.42(3 * 3. 14)= 1 cm