In the diagram above, O is the center if the two concentric circle of radii 13cm and 10cm respectively. Find the area of the shaded portion in the sector with angle 120° at the center
- \(\frac{1}{3}\pi cm^2\)
- \(\pi cm^2\)
- \(3\pi cm^2\)
-
\(23\pi cm^2\)
- \(46\pi cm^2\)
The correct answer is: D
Explanation
\(\frac{120\pi}{360}(R^2 - r^2)\\
\frac{1}{3}\times \pi (13^2 - 10^2)\\
\frac{1}{3}\times \pi \times 69 = 23\pi cm^2\)