Two concentric circles have circumferences in ratio 4:7. If smaller circle has area 80 m², what is the approximate area of the larger circle?

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Accepted Answer

1. The circumference ratio equals the radius ratio, so $r_1:r_2=4:7$.
2. Area scales with square of radius, so area ratio is $4^2:7^2=16:49$.
3. Larger area = $80	imes\dfrac{49}{16}=80	imes3.0625=245$ m$^2$.

FINAL_ANSWER: a

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