2006 AMC 10A Problem 17

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Concepts:coordinate geometryareasquare (geometry)

Difficulty rating: 1540

17.

In rectangle ADEH,ADEH, points BB and CC trisect AD,\overline{AD}, and points GG and FF trisect HE.\overline{HE}. In addition, AH=AC=2.AH = AC = 2. What is the area of quadrilateral WXYZWXYZ shown in the figure?

12\dfrac{1}{2}

22\dfrac{\sqrt{2}}{2}

32\dfrac{\sqrt{3}}{2}

223\dfrac{2\sqrt{2}}{3}

233\dfrac{2\sqrt{3}}{3}

Solution:

Set A=(0,0),A = (0, 0), D=(3,0),D = (3, 0), H=(0,2),H = (0, 2), so B=(1,0),B = (1, 0), C=(2,0),C = (2, 0), G=(1,2),G = (1, 2), F=(2,2),F = (2, 2), and E=(3,2).E = (3, 2).

The drawn segments meet at W=(1.5,1.5),W = (1.5, 1.5), X=(1,1),X = (1, 1), Y=(1.5,0.5),Y = (1.5, 0.5), and Z=(2,1).Z = (2, 1). These form a square whose perpendicular diagonals WYWY and XZXZ each have length 1.1.

Its area is 1211=12.\frac12 \cdot 1 \cdot 1 = \frac12.

Thus, the correct answer is A.

Problem 17 in Other Years