We have the following picture: 
The radius of the larger circle is twice that of the smaller circle. Find an expression for the fraction of the area of the square which is occupied by the two circles.
I know that the area of the 2 circles together is $5 \pi r^2$, but I can't seem to find a way to express the area of the square in terms of $r$. Can I get a hint?
Hint: The diagonal of the square is $2r\sqrt{2}+2r+r+r\sqrt{2}$.