An annular (ring-shaped) disc has outer and inner radii of 12 cm and 8 cm. What percentage of the full circle is this ring?

Question

Accepted Answer

1. Outer area = $\pi	imes12^2=\pi	imes144$.
2. Inner area = $\pi	imes8^2=\pi	imes64$.
3. Ring area = $\pi(144-64)=\pi	imes80$.
4. Fraction of full circle = $\dfrac{\pi	imes80}{\pi	imes144}=\dfrac{80}{144}=\dfrac{5}{9}\approx0.5556$.
5. Percentage = $0.5556	imes100\%=55.56\%$. So the answer is **(b)**.
FINAL_ANSWER: b

Answer

Answer

Answer