Question 77707
Find the area of the region between two concentric circles with radii 9 and 6. 
:
If "concentric" means that the smaller circle is inside the larger circle, then we subtract the area of the smaller circle from the area of the larger circle.
:
The formula for the area of a circle is {{{highlight(A=pi*r^2)}}} A=area, r=radius, pi is approximately 3.141592654
The area of the larger circle with r=9 is: 
{{{A=pi*(9)^2}}} 
{{{A=81*pi}}}
The area of the smaller circle with r=6 is:
{{{A=pi*(6)^2}}}
{{{A=36*pi}}}
The difference is:
{{{81*pi-36*pi=45*pi}}}
You can approximate this to whatever your teacher wants.  A lot will let you use pi=3.14
{{{45*3.14=141.3}}}
Happy Calculating!!!