Curved surface area of a hemisphere, diameter 28 cm: Find the curved surface area (in cm²).
Aptitude
Area
Difficulty: Easy
Choose an option
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A1152
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B1024
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C956
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D1232
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ENone of these
Answer
Correct Answer: 1232
Explanation
Introduction / Context:The curved surface area (CSA) of a hemisphere depends only on the radius via CSA = 2πr^2.
Given Data / Assumptions:
- Diameter = 28 cm ⇒ r = 14 cm.
Concept / Approach:Apply CSA = 2πr^2 directly and evaluate numerically.
Step-by-Step Solution:
1) CSA = 2 * π * 14^2 = 2 * π * 196 = 392π.2) Using π ≈ 22/7 ⇒ CSA = 392 * 22/7 = 56 * 22 = 1232 cm².Verification / Alternative check:Using π ≈ 3.1416 gives ≈ 1231.5, which rounds to 1232.
Why Other Options Are Wrong:1152, 1024, 956 do not equal 392π.
Common Pitfalls:Using sphere area 4πr^2 or including the base area; only curved area is asked.
Final Answer:1232.