Surface area of cones practice answers
1. A cone has a radius of 5 cm and a slant height of 12 cm. What is its surface area?
To find the surface area of a cone, we need to find the curved surface area (CSA) and add it to the base area (BA).
CSA = π * r * l
CSA = π * 5 cm * 12 cm
CSA = 60π cm²
The base area of a cone is given by:
BA = π * r²
BA = π * (5 cm)²
BA = 25π cm²
Surface area = CSA + BA
Surface area = 60π cm² + 25π cm²
Surface area = 85π cm²
Surface area ≈ 267 cm² (rounded to nearest whole number)
The surface area of the cone is approximately 267 cm².
2. A cone has a radius of 8 cm and a slant height of 15 cm. What is its surface area?
CSA = π * r * l
CSA = π * 8 cm * 15 cm
CSA = 120π cm²
BA = π * r²
BA = π * (8 cm)²
BA = 64π cm²
Surface area = CSA + BA
Surface area = 120π cm² + 64π cm²
Surface area = 184π cm²
Surface area ≈ 577 cm² (rounded to nearest whole number)
The surface area of the cone is approximately 577 cm².
3. A cone has a radius of 3.5 cm and a slant height of 10 cm. What is its surface area?
CSA = π * r * l
CSA = π * 3.5 cm * 10 cm
CSA = 35π cm²
BA = π * r²
BA = π * (3.5 cm)²
BA = 12.25π cm²
Surface area = CSA + BA
Surface area = 35π cm² + 12.25π cm²
Surface area = 47.25π cm²
Surface area ≈ 148 cm² (rounded to nearest whole number)
The surface area of the cone is approximately 148 cm².