Sphere with given surface area — compute volume exactly: If a sphere has surface area 616 sq cm, find its volume (in cubic centimeters).

Difficulty: Easy

Correct Answer: 4312/3 cm3

Explanation:


Introduction / Context:
Given a sphere’s surface area, solve for its radius and then compute the volume. The numbers are chosen so that using π = 22/7 leads to exact integer simplification.



Given Data / Assumptions:

  • S = 4πr^2 = 616 cm2.
  • π = 22/7 (standard in such aptitude items).
  • Volume V = (4/3)πr^3.


Concept / Approach:
From 4πr^2 = 616, obtain r first. Then substitute into V = (4/3)πr^3 and simplify exactly.



Step-by-Step Solution:
r^2 = 616/(4π) = 154/π = 154 * 7/22 = 49 ⇒ r = 7 cmV = (4/3)πr^3 = (4/3)π * 343 = (1372/3)πWith π = 22/7: V = (1372/3) * (22/7) = (196 * 22)/3 = 4312/3 cm3



Verification / Alternative check:
Decimal check: 4312/3 ≈ 1437.33 cm3, reasonable for r = 7 cm.



Why Other Options Are Wrong:
Other fractions do not match the exact cancellation with r = 7 and π = 22/7.



Common Pitfalls:
Using 616/π as if it were 616/3.14 with premature rounding; mis-evaluating r from S.



Final Answer:
4312/3 cm3

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