Problem:
Circles with centers A and B have radii 3 and 8 , respectively. A common internal tangent intersects the circles at C and D, respectively. Lines AB and CD intersect at E, and AE=5. What is CD?
Answer Choices:
A. 13
B. 344β
C. 221β
D. 255β
E. 355β Solution:
Radii AC and BD are each perpendicular to CD. By the Pythagorean Theorem,
CE=52β32β=4
Because β³ACE and β³BDE are similar,
CEDEβ=ACBDβ, so DE=CEβ ACBDβ=4β 38β=332β