Problem: Circle I is circumscribed about a given square and circle II is inscribed in the given square. If r is the ratio of the area of circle I to that of circle II, then r equals:
Answer Choices:
A. 2​
B. 2
C. 3​
D. 22​
E. 23​
Solution:
Let s be the length of a side of the square. The radius of circle I is 21​s2​ and its area K1​=21​πs2. The radius of circle II is 21​s and its area K2​=41​πs2.∴r=K2​K1​​=2