Question

A ring-shaped metallic sheet has outer and inner radii 10 cm and 6 cm. What percentage of the full circle's area is the ring?

• A. 36%
• B. 48%
• C. 64%
• D. 76%

Answer 1

Answer:

C. 64%

Outer radius (R = 10) cm, inner radius (r = 6) cm.

Area of full circle (outer circle)

$A_{\text{outer}} = \pi R^2 = \pi \times 10^2 = 100\pi$

Area of inner circle

$A_{\text{inner}} = \pi r^2 = \pi \times 6^2 = 36\pi$

Area of ring

$A_{\text{ring}} = 100\pi - 36\pi = 64\pi$

Percentage of full circle occupied by ring

$\frac{64\pi}{100\pi} \times 100 = 64\%$

Final Answer

$\boxed{64\%}$