1. Volume of Cones Lesson 21

2. 1. Sketch and label a diagram of a cone with a radius of 3 cm and a height of 7 cm. 2. Find the surface area of the cone in #1. 3. A cone and a cylinder have congruent bases and are the same height. Predict what the relationship between their volumes will be.

3. Target: Calculate the volume of cones.

4. The volume of a cone is equal to one-third of the product of the area of the base (B) and the height (h).

5. Find the volume of the cone. Use 3.14 for π.  Write the formula.V = πr 2 h  Substitute known values.V ≈ (3.14)(4) 2 (12)  Find the value of the power.V ≈ (3.14)(16)(12)  Multiply.V ≈ 200.96  The volume of the cone is about 200.96 cm 3.

6. Chantel helped with her sister’s party. Each child received a party hat full of treats. Each hat had a volume of 65.94 cubic inches. The radius of each hat was 3 inches. How tall was each party hat?  Write the formula. V = πr 2 h  Substitute known values. 65.94 ≈ (3.14)(3) 2 h  Find the value of the power.65.94 ≈ (3.14)(9)h  Multiply. 65.94 ≈ 9.42h  Divide by 9.42 on both sides. 9.42 9.42 7 ≈ h  Each party hat was about 7 inches tall.

7. 1. Find the volume of the cone. Use 3.14 for . 2. A cone has a volume of 30 cubic inches. What is the volume of a cylinder with the same height and a congruent base to the cone?

8. What is similar about cones and pyramids? What is different?