Concentric Circles Area

The small circle in the picture has an area of 3.5 cm². It touches from the inside and passes through the center of the large circle. What is the area of a large circle? The result round to an integer.

Final Answer:

S₂ =  14 cm²

Step-by-step explanation:

$$\begin{gathered} S_1=3.5{\text{cm}}^2 \\ {S}_1=\pi r_1^2 \\ {r}_1=\sqrt{S_1/\pi }=\sqrt{3.5/3.1416}\doteq 1.0555\text{cm} \\ {r}_2=2\cdot r_1=2\cdot 1.0555\doteq 2.111\text{cm} \\ {S}_2=\pi \cdot r_2^2=3.1416\cdot 2.111^2=14{\text{cm}}^2 \end{gathered}$$

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