Problem

2006 AMC 10B Problem 24

Circles with centers O and P have radii 2 and 4, respectively, and are externally tangent. Points A and B on the circle with center O and points C and D on the circle with center P are such that AD and BC are common external tangents to the circles. What is the area of the concave hexagon AOBCPD?

[asy] unitsize(.7cm); defaultpen(.8); pair O = (0,0), P = (6,0), Q = (-6,0); pair A = intersectionpoint( arc( (-3,0), (0,0), (-6,0) ), circle( O, 2 ) ); pair B = (A.x, -A.y ); pair D = Q + 2*(A-Q); pair C = Q + 2*(B-Q); draw( circle(O,2) ); draw( circle(P,4) ); draw( (Q + 0.8*(A-Q)) -- ( Q + 2.3*(A-Q) ) ); draw( (Q + 0.8*(B-Q)) -- ( Q + 2.3*(B-Q) ) ); draw( A -- O -- B ); draw( C -- P -- D ); draw( O -- P ); label("$O$",O,W); label("$P$",P,E); label("$A$",A,NNW); label("$B$",B,SSW); label("$D$",D,NNW); label("$C$",C,SSW); [/asy]

\mathrm{(A) \ } 18\sqrt{3}\qquad \mathrm{(B) \ } 24\sqrt{2}\qquad \mathrm{(C) \ } 36\qquad \mathrm{(D) \ } 24\sqrt{3}\qquad \mathrm{(E) \ } 32\sqrt{2}

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.


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Category: AMC 10B
Points: 4
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