Difficulty: Medium
Correct Answer: 4158 sq. cm
Explanation:
Introduction / Context:
For a hemisphere, volume V = (2/3)πr^3 and total surface area (TSA) = 3πr^2 (curved area + base).
Given Data / Assumptions:
Concept / Approach:
Find r from volume, then compute TSA.
Step-by-Step Solution:
(2/3)πr^3 = 19404 ⇒ (44/21)r^3 = 19404 ⇒ r^3 = 19404 * 21 / 44 = 441 * 21 = 9261 = 21^3r = 21 cmTSA = 3πr^2 = 3 * (22/7) * 441 = 66 * 63 = 4158 sq. cm
Verification / Alternative check:
Back-substitute r into volume: (2/3)*(22/7)*9261 = 19404 ✔
Why Other Options Are Wrong:
27772 is far too large; 5544 and 1386 mismatch 3πr^2.
Common Pitfalls:
Using curved area 2πr^2 instead of TSA 3πr^2.
Final Answer:
4158 sq. cm
Discussion & Comments