AMC 10 Step by Step
2025 AMC 10AProblem 22P21-25~7 minPrint

A circle of radius rr is surrounded by three circles, whose radii are 1, 2, and 3, all externally tangent to the inner circle and externally tangent to each other, as shown in the diagram below.

figure

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.