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