Okay, this is really bugging me:
My Math book has this practice where I need to get the area and perimeter of the next Circular Crown:
$R = 3$cm , $r = 1.75$cm.
Well, I do it. But my results are simply different than the ones the book tells me (on the back of the book, there is an answers sheet). Why? The process to get the area and perimeter are relatively simple. The instructions are on the book. I follow them, and I fail!
Now, my Math teacher told me it was because [put reason here], but it was ages ago, and I can't remember. I remember the book is right, but I forgot why and how.
The book says that the area is $5.94\pi^2$ and the perimeter is $9.5\pi$. However, I get the area is $\frac{95}{16}\pi$ and the perimeter is $\frac{19}{2}\pi$.
What am I doing wrong?