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algebra intermediate
Problem
Let points , , , and . Quadrilateral is cut into equal area pieces by a line passing through . This line intersects at point , where these fractions are in lowest terms. What is ?
(A)
(B)
(C)
(D)
Solution
First, we shall find the area of quadrilateral . This can be done in any of three ways: Pick's Theorem: Splitting: Drop perpendiculars from and to the x-axis to divide the quadrilateral into triangles and trapezoids, and so the area is Shoelace Theorem: The area is half of , or . . Therefore, each equal piece that the line separates into must have an area of . Call the point where the line through intersects . We know that . Furthermore, we know that , as . Thus, solving for , we find that , so . This gives that the y coordinate of E is . Line CD can be expressed as , so the coordinate of E satisfies . Solving for , we find that . From this, we know that .
Final answer
B