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Everyone reasoned in a similar way:
Area of circle $=\pi r^2$
Area of the largest circle $= \pi \times 7^2 = 49 \pi cm^2$
Area of the red ring $= \pi \times 4^2 - \pi \times 3 ^ 2 = 7 \pi cm^2$
$\frac{7}{49}= \frac{1}{7}$
The red ring is $\frac{1}{7}$ of the whole circle.
Area of the green ring $= \pi \times 6^2 - \pi \times 5^2 = 11 \pi cm^2$
The green ring is $\frac{11}{49}$ of the whole circle.