Surface area of a cylinder = 2 × area of base + lateral surface area
Area of base = πr², lateral surface area = 2πr×h (h is the height)
📘 Example ①
Find the surface area of a cylinder with a base radius of 3 cm and a height of 4 cm.
Answer: Area of base = π×3² = 9π. Lateral surface area = 2π×3×4 = 24π.
Surface area = 9π×2 + 24π = 18π + 24π = 42π cm²
Find the surface area of a cylinder with a base radius of 3 cm and a height of 4 cm.
Answer: Area of base = π×3² = 9π. Lateral surface area = 2π×3×4 = 24π.
Surface area = 9π×2 + 24π = 18π + 24π = 42π cm²
💡 Key Points
- Cylinder: 2 bases (πr² ×2) + lateral surface (2πr×h)
- Keep π in the answer while calculating
Practice Problem
- Find the surface area of a cylinder with a base radius of 5 cm and a height of 8 cm (leave π as it is).
Answer and Explanation
- Answer: 130π cm². Area of bases=25π×2=50π. Lateral surface area=2π×5×8=80π. Total=130π.