Question

Please I need help my teacher told me to do 3.14 x 81 but it’s wrong

Answer 1

well, let's take a looksie, hmm the sector is really a sector with a central angle of 90°, wait a second!! a circle has a total of 360°, so 90°+90°+90°+90° = 360°, so 90°is really just one quarter that of a circle.

Now, if we just get the whole area of the circle, then grab only one quarter of that, we'll be set, yeahhhh!!

`\textit{area of a circle}\\\\ A=\pi r^2 ~~ \begin{cases} r=radius\\[-0.5em] \hrulefill\\ r=9 \end{cases}\implies A=\pi (9)^2 \\\\\\ \stackrel{\textit{one quarter of that}}{\cfrac{1}{4}\cdot \pi (9)^2}\implies \cfrac{81\pi }{4}\implies \cfrac{81(3.14)}{4} ~~ \approx ~~ \text{\LARGE 63.6}`