Verified Answer :

\(A_1=\pi r^2\\\\R=2r\ then\ A_2=\pi R^2\to A_2=\pi(2r)^2=4\pi r^2\\\\A_2-A_1=4\pi r^2-\pi r^2=3\pi r^2=3A_1\\\\3=300\%\\\\Answer:(C).\)

sugahsweetieh

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