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2007 AMC 10BProblem 18P16-20~4 minPrint
CirclesTriangles: Area & PythagoreanAdd construction lines/points (drop altitudes, extend segments, connect centers)Set up the equation/formula and compute; no special trick needed

A circle of radius 11 is surrounded by 44 circles of radius rr as shown. What is rr ?
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Problem © Mathematical Association of America (MAA), American Mathematics Competitions. Reproduced for non-commercial educational use. Solution and commentary are original to this site.