



 
Hi George, I think the equation of the smaller circle is $x^2 + y^2 = 25.$ A circle with centre at the origin and radius $r$ has equation $x^2 + y^2 = r^2$ and thus the smaller circle has radius 5 units. Here is my diagram. $C$ is the origin. Triangle $ABC$ is a right triangle and $AB = BC = 5.$ Use Pythagoras' theorem to find the length of $CA.$ This is the radius of the larger circle. Can you complete the problem now? Rather than asking for the dimensions of the larger square I would have asked for the length of its diagonal. Can you find the length of the diagonal? Penny  


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