Difficulty: Easy
Correct Answer: 3 cm
Explanation:
Introduction / Context:
The curved (lateral) surface area of a cylinder is the rectangle that wraps around: width equals the height h and length equals the circumference 2πr. This question checks algebraic manipulation of the CSA formula to recover r from given CSA and h.
Given Data / Assumptions:
Concept / Approach:
Rearrange 2πrh = CSA to r = CSA / (2πh). Substitute numeric values carefully and simplify.
Step-by-Step Solution:
2πh = 2 * 3.14 * 5 = 31.4r = 94.2 / 31.4 = 3.0 cm
Verification / Alternative check:
Plug back: 2πrh = 2 * 3.14 * 3 * 5 = 94.2 cm^2, matching exactly.
Why Other Options Are Wrong:
5 cm and 4 cm make CSA too large; 8 cm is far too large; 2 cm would give only 62.8 cm^2, not 94.2 cm^2.
Common Pitfalls:
Using πr^2h (volume) instead of 2πrh (CSA); multiplying by diameter in place of radius; rounding too early.
Final Answer:
3 cm
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