Cube with equal surface area and volume (numerically) — find edge length: If the numerical value of the volume (in unit^3) equals the numerical value of the surface area (in unit^2) of a cube, what is the edge length of the cube in units?
Aptitude
Volume and Surface Area
Difficulty: Easy
Choose an option
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A3
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B4
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C5
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D6
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ENone of these
Answer
Correct Answer: 6
Explanation
Introduction / Context:For a cube of edge a, the volume is a^3 and total surface area is 6a^2. The question states their numerical values are equal, which allows solving directly for a.
Given Data / Assumptions:
- Volume V = a^3
- Surface area S = 6a^2
- Numerical equality: a^3 = 6a^2 with a > 0
Concept / Approach:Divide both sides by a^2 (a ≠ 0) to isolate a.
Step-by-Step Solution:a^3 = 6a^2 ⇒ a = 6
Verification / Alternative check:Check: volume 216 and surface area 216 (units differ but numbers match) satisfies the condition.
Why Other Options Are Wrong:No other integer satisfies a^3 = 6a^2 for positive a.
Common Pitfalls:Treating units as needing to match; only numerical equality is required here.
Final Answer:6