Percent increase in cube surface area when side doubles: When each edge of a cube is doubled, by what percentage does its total surface area increase?
Aptitude
Volume and Surface Area
Difficulty: Easy
Choose an option
-
A150%
-
B300%
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C50%
-
D25%
Answer
Correct Answer: 300%
Explanation
Introduction / Context:Surface area of a cube scales with the square of its edge. Doubling the edge multiplies surface area by 4, leading to a specific percentage increase. This is a scaling/ratio question.
Given Data / Assumptions:
- Original edge a, SA1 = 6a^2
- New edge 2a, SA2 = 6*(2a)^2 = 24a^2
Concept / Approach:
- Percent increase = ((SA2 − SA1) / SA1) * 100%.
Step-by-Step Solution:
Increase = 24a^2 − 6a^2 = 18a^2.Percent increase = (18a^2 / 6a^2) * 100% = 3 * 100% = 300%.Verification / Alternative check:
Pick a = 1: SA1=6; SA2=24; increase 18 on base 6 ⇒ 300%.Why Other Options Are Wrong:
- 150%/50%/25%: These correspond to edge, area, or linear misinterpretations.
Common Pitfalls:
- Assuming surface area doubles when edge doubles (it quadruples).
Final Answer:
300%