Problem: The area of the ring between two concentric circles is 1221βΟ square inches. The length of a chord of the larger circle tangent to the smaller circle, in inches, is:
Answer Choices:
A. 2β5β
B. 5
C. 52β
D. 10
E. 102β
Solution:
Let R be the larger radius, let r be the smaller radius, and let L (inches) be the length of the chord. Then R2βr2=(2Lβ)2. Since ΟR2βΟr2=225Οβ,R2βr2=225β.