Jasontuyj2012 wrote:

In the figure below, a circle is inscribed in a square with side b and a square with side a is inscribed in the circle. What is the area of the square with side b?

(1) a = 4

(2) the radius of the circle is 2 radical sign 2

Visualizing the diagram that:

The diagonal of the small square = diameter of the circle = the side of the bigger square.

From 1, b = the side (b) of the bigger square = diameter of the circle (d = 2r) = a (sqrt2) = 4 (sqrt2). Sufficient.

From 2, If r = 2 (sqrt2), d = 4 (sqrt 2), which is equal to the side (b) of the bigger square. Sufficinet..

So it is D..