Cone — Vertical height 24 cm and volume 1232 cm^3. Find the curved surface area (CSA).
Aptitude
Volume and Surface Area
Difficulty: Medium
Choose an option
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A1254 cm2
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B704 cm2
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C550 cm2
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D154 cm2
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E616 cm2
Answer
Correct Answer: 550 cm2
Explanation
Introduction / Context:Given cone volume and height, find radius, then slant height and CSA. Use V = (1/3)πr^2h, l = √(r^2 + h^2), CSA = π r l.
Given Data / Assumptions:
- h = 24 cm
- V = 1232 cm^3
- Use π = 22/7 for neat integers
Concept / Approach:Compute r from 8πr^2 = 1232 (since (1/3)*24 = 8), then l, then CSA.
Step-by-Step Solution:8πr^2 = 1232 ⇒ r^2 = 154/π = 49 (with π = 22/7) ⇒ r = 7 cml = √(r^2 + h^2) = √(49 + 576) = √625 = 25 cmCSA = π r l = (22/7) * 7 * 25 = 550 cm2
Verification / Alternative check:Volume back-check: (1/3)*π*7^2*24 = 1232 cm^3 ✔
Why Other Options Are Wrong:704, 616, 1254, and 154 cm2 result from arithmetic or formula mix-ups.
Common Pitfalls:Using height instead of slant height in CSA.
Final Answer:550 cm2