Question 550970
<pre>
 
I assume the figure is like this

{{{drawing(200,200,-1.2,1.2,-1.2,1.2,

line(-1,-1,1,-1),line(1,-1,1,1),line(1,1,-1,1),line(-1,1,-1,-1),
arc(1,0,2,-2,90,270),arc(-1,0,2,-2,270,450)


 )}}}

And the shaded area is this apple core: {{{drawing(200,200,-1.2,1.2,-1.2,1.2,

line(-1,-1,1,-1),line(1,1,-1,1),
arc(1,0,2,-2,90,270),arc(-1,0,2,-2,270,450)


 )}}}



The rectangle is a square with side 9, so its area is 9² or 81 sq.ft.

The two semicircles make 1 complete circle, with diameter 9, which
means its radius is {{{9/2}}} and the area is <font face = "symbol">p</font>r²
or <font face = "symbol">p</font>{{{(9/2)^2}}} or {{{81/4}}}<font face = "symbol">p</font>.

So if we subtract the circle's area from the square's area, we get

81 - {{{81/4}}}<font face = "symbol">p</font> =

81 - {{{81/4}}}×3.14

81 - 20.25×3.14

81 - 63.585

17.415 sq.ft.

Edwin</pre>