Trapezoid Riddle III

Geometry Level 1

In trapezoid A B C D , ABCD, A B C D AB || CD and point E E as the midpoint of side A D , AD, as shown below.

Which area is larger?

Red Blue Both are equal Not enough information

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1 solution

If we draw the extending lines, parallel to segments A D AD and D C DC , to meet at point G G , as shown above, we will create a parallelogram A G C D AGCD . Then if we draw B F BF parallel to A E AE , it is also obvious that A B F E ABFE is another parallelogram, thus making the areas of triangles A B E ABE = B F E BFE because B E BE is the diagonal of the parallelogram.

Thereby, since E E is the midpoint of A D AD , the segments B F = H C BF = HC and B I = I C BI = IC because of parallel rules. Moreover, since B I F = H I C \angle BIF = \angle HIC for the intersection angles, the triangles B I F BIF and H I C HIC are congruent, thus having the same area.

As a result, we can virtually demonstrate the area equality as two bisected parallelograms, as shown below:

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