The radius of a right circular cone is 3.5 cm and slant height is 0.21 m, then what is its lateral surface area? (Use )
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Correct answer: A
Explanation
The correct answer is option 1 i.e. 231 cm2 .
Radius r = 3.5 cm
Slant height l = 0.21 m = 0.21 × 100 = 21 cm
Lateral surface area of cone = π × r × l
= (22/7) × 3.5 × 21
= (22/7) × (7/2) × 21 (because 3.5 = 7/2)
= 11 × 21 = 231 cm2