story problem

Question

The area of a circle with radius r is given by the formula A=π r²  . If a circle has area 169π square inches, what is the radius?

Answer 1

Divide by \pi and take a square root.

 

 

Alternatively if we set \pi*r^2=169*\pi

then r^2=169, and so r=13, as 13^2=169.