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2007 AMC 12B Question 22

AMC12 · 2007 AMC 12B

Question 22

Two particles move along the edges of equilateral $\triangle ABC$ in the direction $$
A\to B\to C\to A,
$$ starting simultaneously and moving at the same speed. One starts at $A,$ and the other starts at the midpoint of $\overline{BC}.$ The midpoint of the line segment joining the two particles traces out a path that encloses a region $R.$ What is the ratio of the area of $R$ to the area of $\triangle ABC?$
  1. $\dfrac{1}{16}$
  2. $\dfrac{1}{12}$
  3. $\dfrac{1}{9}$
  4. $\dfrac{1}{6}$
  5. $\dfrac{1}{4}$