The radius of a sphere is 21 cm. It is cut into two halves by a plane passing through its center. What is 75% of the curved surface area (in cm2, rounded off to the nearest tens) of the hemisphere? ()
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e. 2080.
Given that
The radius of the sphere (r) = 21 cm
It is cut into two halves by a plane passing through its center,
We know that,
The CSA of hemisphere = 2πr2
Now,
The curved surface area = 2 × (22/7) × 212 = 2772
Hence, the 75% curved surface area = 0.75 × 2772 = 2079 ≈ 2080 cm2