Right circular cone — Base radius 6 cm and slant height 28 cm. Find the curved surface area (CSA).
Aptitude
Volume and Surface Area
Difficulty: Easy
Choose an option
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A268 sq. cm
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B528 sq. cm
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C462 sq. cm
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D658 sq. cm
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E396 sq. cm
Answer
Correct Answer: 528 sq. cm
Explanation
Introduction / Context:Curved surface area (CSA) of a cone is π r l, where r is base radius and l is slant height.
Given Data / Assumptions:
- r = 6 cm
- l = 28 cm
Concept / Approach:Direct substitution into CSA = π r l.
Step-by-Step Solution:CSA = π * 6 * 28 = 168π ≈ 528 sq. cm (using π ≈ 22/7)
Verification / Alternative check:168 * (22/7) = 168 * 3.142857… = 528 exactly with 22/7.
Why Other Options Are Wrong:462 corresponds to π * r^2 or other mix-ups; 268 and 396 are underestimates; 658 is an overestimate.
Common Pitfalls:Using height instead of slant height in π r l.
Final Answer:528 sq. cm