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geometry junior
Problem
A circle with radius is inscribed in a square and circumscribed about another square as shown. Which fraction is closest to the ratio of the circle's shaded area to the area between the two squares? 
(A)
(B)
(C)
(D)
Solution
The area of the smaller square is one half of the product of its diagonals. Note that the distance from a corner of the smaller square to the center is equivalent to the circle's radius so the diagonal is equal to the diameter: The circle's shaded area is the area of the smaller square subtracted from the area of the circle: If you draw the diagonals of the smaller square, you will see that the larger square is split congruent half-shaded squares. The area between the squares is equal to the area of the smaller square: Approximating to the ratio of the circle's shaded area to the area between the two squares is about
Final answer
A