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1999 AMC 12 Question 26

AMC12 · 1999 AMC 12

Question 26

Three non-overlapping regular plane polygons, at least two of which are congruent, all have sides of length $1.$ The polygons meet at a point $A$ in such a way that the sum of the three interior angles at $A$ is $360^\circ.$ Thus the three polygons form a new polygon with $A$ as an interior point. What is the largest possible perimeter that this polygon can have?
  1. $12$
  2. $14$
  3. $18$
  4. $21$
  5. $24$