Question 466105
<pre>
{{{drawing(400,400,-11,11,-11,11,

circle(0,0,10),circle(-5,0,5),
locate(-5,0,B), locate(0,0,A),
line(-5,0,0,0), locate(-2.5,0,5)

 )}}}

The area of the larger circle is found with formula:

A = <font face = "symbol">p</font>r²

The radius of the larger circle is 10 units,

so its area is

A = <font face = "symbol">p</font>(10)² = <font face = "symbol">p</font>*100 = 100<font face = "symbol">p</font> square units.

----

The area of the smaller circle is also found with formula 

A = <font face = "symbol">p</font>r²

The radius of the smaller circle is 5 units.

so its area is

A = <font face = "symbol">p</font>(5)² = <font face = "symbol">p</font>*15 = 25<font face = "symbol">p</font> square units.

----

Therefore when we remove the small circle, the area that's left is

 
100<font face = "symbol">p</font> - 25<font face = "symbol">p</font> square units, or

(100-25)<font face = "symbol">p</font> square units or

75<font face = "symbol">p</font> square units or approximately 235.6 square units.

Edwin</pre>