Problem:
Circles with centers A and B have radii 3 and 8, respectively. A common internal tangent touches the circles at C and D, as shown. Lines AB and CD intersect at E, and AE=5. What is CD?
Answer Choices:
A. 13
B. 344
C. 221
D. 255
E. 355
Solution:
Radii AC and BD are each perpendicular to CD. By the Pythagorean Theorem,
