PROBLEM 2

Six pennies are arranged in a triangle: one penny touching each oftwo pennies below it, and these two on top of a row of three pennies at thebottom. Each penny is tangent to the two below it and to those to its left orright:o
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Another penny starts directly at the left of the bottom row, tangent to thepenny on the left, and rolls around the triangle without slipping, alwaystangent to at least one penny. How many revolutions about its own centre doesthis penny make by the time it returns to its starting position?

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