## Tangent CirclesTrick brain teasers appear difficult at first, but they have a trick that makes them really easy.Four circles are situated in the plane so that each is tangent to the other three.
If three of the radii are 3, 4, and 5, what's the largest possible radius of the fourth circle? ## AnswerThe four circles can be tangent to each other at the same point, therefore there is no upper bound to the radius of the fourth circle!Hide ## What Next?
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