Equal areas: circle vs square — compare diameter and diagonal: If a circle and a square have equal areas, what is (diameter of circle / diagonal of square)^2?
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A11/7
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B7/9
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C7/11
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D9/7
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E2/π
Answer
Correct Answer: 7/11
Explanation
Introduction / Context:Equate the areas to relate the circle radius to the square side. Then express the requested squared ratio in those terms. Using π = 22/7 gives a clean rational result matching options.
Given Data / Assumptions:
- Area(circle) = Area(square).
- Let circle radius = r, square side = s.
- Use π = 22/7 for final numeric comparison to options.
Concept / Approach:πr^2 = s^2 ⇒ (diameter/diagonal)^2 = (2r / (s√2))^2 = (4r^2)/(2s^2) = 2r^2/s^2 = 2/π.
Step-by-Step Solution:
From equality: s^2 = πr^2.(diameter/diagonal)^2 = 2r^2 / s^2 = 2 / π.With π = 22/7, 2/π = 2 / (22/7) = 14/22 = 7/11.Verification / Alternative check:Direct substitution with any r (e.g., r = 1) produces the same 2/π expression; rationalizing with 22/7 yields 7/11.
Why Other Options Are Wrong:11/7 and 9/7 invert the correct value; 7/9 mismatches; 2/π is the unsimplified exact form but the keyed answer is its 22/7 evaluation.
Common Pitfalls:Comparing diameter to side (not diagonal), or forgetting the √2 for the square’s diagonal.
Final Answer:7/11