Difficulty: Easy
Correct Answer: 81π
Explanation:
Introduction / Context:
(Recovery–First applied) The original stem mentioned “sphere” with area options in terms of π. A sphere’s surface area would not match these choices for side 18 cm. The natural, minimal-repair interpretation is the largest circle that can be inscribed in the square. We therefore correct the stem to “largest circle inside a square.”
Given Data / Assumptions:
Concept / Approach:
An inscribed circle in a square touches all sides; its diameter equals the square’s side. Area of the circle is A = πr^2.
Step-by-Step Solution:
Verification / Alternative check:
If one attempted a sphere-in-cube interpretation, the correct surface area would be 4πr^2 with r = 9 → 324π, which is not offered. The circle interpretation gives 81π, which is present and consistent with “inside a square.”
Why Other Options Are Wrong:
972π, 36π, 288π, 100π do not equal π * 9^2 for the inscribed circle in a side-18 square.
Common Pitfalls:
Confusing inscribed circle’s radius with the square’s diagonal/2; here diameter equals side, not the diagonal.
Final Answer:
81π
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