Surface area of a sphere with radius 4 cm: Compute the total surface area (in square centimeters).

Aptitude Volume and Surface Area Difficulty: Easy
Choose an option
  • A
    64π sq cm
  • B
    69π sq cm
  • C
    32π sq cm
  • D
    35π sq cm
  • E
    48π sq cm

Answer

Correct Answer: 64π sq cm

Explanation

Introduction / Context:This is a straightforward substitution into the sphere surface area formula. The test is about using 4πr^2, not 2πr or 4/3πr^3.

Given Data / Assumptions:

  • r = 4 cm
  • Surface area S = 4πr^2

Concept / Approach:Compute r^2 and multiply by 4π to keep the answer in exact π form as options are given with π.

Step-by-Step Solution:S = 4π * 16 = 64π sq cm

Verification / Alternative check:Numeric check: with π ≈ 3.1416, S ≈ 201.06 cm^2, consistent with 64π.

Why Other Options Are Wrong:69π, 35π, 48π are unrelated; 32π is half the correct value (confusing with 2πr^2, which is not a standard formula).

Common Pitfalls:Using circumference or volume formulas instead of surface area; mis-squaring 4 as 4 rather than 16.

Final Answer:64π sq cm

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