Question

Find the area of the shaded parts.

Answer 1

12πin² = 37.7in² (3sf)

Explanation:

area of whole circle = π(4)² = 16π

area of small circle = π(2)² = 4π

area of shaded = 16π - 4π = 12π

12π = 37.6991... ≈ 37.7in² (3sf)

Answer 2

`\textit{area of a circular ring}\\\\ A=\pi (R^2 - r^2) ~~ \begin{cases} R=\stackrel{outer}{radius}\\ r=\stackrel{inner}{radius}\\[-0.5em] \hrulefill\\ R=4\\ r=2 \end{cases}\implies A=\pi (4^2 - 2^2) \\\\\\ A=12\pi \implies A\approx 37.70~in^2`