## Problem of the Week 1137## A 13 Cent ProblemThere are just two essentially different ways of arranging two nickels and three pennies in a ring so that each coin is tangent to two others and all five coins are externally tangent to a circle inside the ring.
For which arrangement is the radius of the inner circle larger?
While it is possible to answer the question knowing only that a nickel is larger than a penny, it is worthwhile to work out the radii in the two cases. The official radius of a U.S. penny is © Copyright 2010 Stan Wagon. Reproduced with permission. |

9 November 2010