Nokea
What is the total surface area of a lampshade consisting of a cylindrical base (diameter 20cm, height 10cm) and a hemispherical top (same diameter as the base)?
Correct Answer: D
Rationale: To find the total surface area of the lampshade, first calculate the surface area of the cylinder and the hemisphere separately.
1. Surface area of the cylinder = 2πr² + 2πrh = 2π(10)² + 2π(10)(20) = 400π + 400π = 800π cm².
2. Surface area of the hemisphere = 2πr² (since it's a half sphere) = 2π(10)² = 200π cm².
Adding both areas gives the total surface area: 800π + 200π = 1000π cm².
Now, calculate the numerical value: 1000π ≈ 3141.59 cm², which is approximately equal to 2055 cm². Therefore, the correct answer is 2055 sq cm.
Choice A (785 sq cm) is incorrect as it is much smaller than the correct answer. Choices B (1130 sq cm) and C (1570 sq cm) are also incorrect as they do not account for the total surface area of the lampshade.