Square from twice the rectangle’s perimeter; semicircle with diameter equal to the square’s side: A rectangle has dimensions 8 cm by 7 cm. A square has perimeter equal to twice the rectangle’s perimeter. Find the perimeter of the semicircle (curved arc + diameter) whose diameter equals the side of that square.
Aptitude
Area
Difficulty: Easy
Choose an option
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A55.12 cm
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B22.54 cm
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C42.51 cm
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D38.57 cm
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ENone of these
Answer
Correct Answer: 38.57 cm
Explanation
Introduction / Context:Convert a rectangle’s perimeter to a square’s perimeter to deduce the square’s side. Then compute a semicircle’s perimeter when its diameter equals that side.
Given Data / Assumptions:
- Rectangle: 8 cm by 7 cm ⇒ perimeter P_rect = 2(8+7) = 30 cm.
- Square perimeter = 2 * P_rect = 60 cm ⇒ side s = 60/4 = 15 cm.
- Semicircle with diameter d = s = 15 cm.
Concept / Approach:Perimeter of a semicircle (including the straight diameter) = (πd)/2 + d.
Step-by-Step Solution:
1) d = 15 cm.2) Arc length = (π*15)/2 ≈ 23.56 cm (π ≈ 3.1416).3) Total perimeter = 23.56 + 15 ≈ 38.56 cm ≈ 38.57 cm.Verification / Alternative check:Using π ≈ 22/7 yields 38.571… cm, matching the option.
Why Other Options Are Wrong:They correspond to using only the arc or incorrect substitutions for d.
Common Pitfalls:Confusing “circumference of semicircle” with arc-only; here perimeter explicitly includes the diameter.
Final Answer:38.57 cm.