AMC 10B 2024 (Problem 10)
Quadrilateral is a parallelogram, and is the midpoint of the side . Let be the intersection of lines and . What is the ratio of the area of quadrilateral to the area of ?


By alternate interior angles,
By vertically opposite angles,
By AA similarity,
Let . Then

Since is a trapezoid with , the triangles and have equal areas:
Let their common area be .

Let their common area be .

Triangles and have the same altitude to line . Therefore,
Hence,

Hence,

Since is a parallelogram, diagonal divides it into two triangles of equal area:
Thus,
Thus,

(A)
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