Difficulty: Easy
Correct Answer: 144
Explanation:
Introduction / Context:
The boundary length of a semicircle includes the curved arc plus the diameter. The standard formula is Perimeter = (1/2 of circumference) + diameter = πr + 2r.
Given Data / Assumptions:
Concept / Approach:
Compute the arc component πr and add the straight diameter 2r. Avoid using the full circumference 2πr, since we only have half the circle plus the diameter.
Step-by-Step Solution:
Verification / Alternative check:
Using π ≈ 3.14 gives 3.14*28 + 56 ≈ 87.92 + 56 ≈ 143.92, rounding to 144, consistent with exact form.
Why Other Options Are Wrong:
288 doubles the arc; 121 and 242 are unrelated to πr + 2r with r = 28 cm; only 144 matches.
Common Pitfalls:
Forgetting to include the diameter or mistakenly halving 2πr to πr and then halving again causes errors.
Final Answer:
144
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