A hemisphere is exactly half of a sphere. In Class 9 and 10 Mensuration, you need to know two important surface area formulas for a hemisphere.
CSA of Hemisphere: 2πr².
TSA of Hemisphere: 3πr².
Volume of Hemisphere: (2/3)πr³.
The extra πr² in TSA comes from the flat circular bottom face.
Let r = radius of the hemisphere.
Curved Surface Area (CSA) = Half the surface area of a sphere = 2πr² (Only the curved dome part, not the flat circular base.)
Total Surface Area (TSA) = Curved Surface Area + Area of circular base = 2πr² + πr² = 3πr²
Find the TSA of a hemisphere with radius = 7 cm. TSA = 3πr² = 3 × (22/7) × 7 × 7 = 3 × 22 × 7 = 462 cm²
CSA = 2πr² = 2 × (22/7) × 7 × 7 = 308 cm²
Volume = (2/3)πr³
TSA of hemisphere = 3πr², where r is the radius.
CSA (2πr²) includes only the curved dome surface. TSA (3πr²) includes the dome plus the flat circular base (πr²).
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