ABCD is a trapezium in which AB is parallel to CD. The sides AD and BC when extended, intersect at point E. If AB = 2 cm, CD = 1 cm, and perimeter of ABCD is 6 cm, then the perimeter, in cm, of $\triangle$AEB is:
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In such geometry problems with a trapezium and intersecting non-parallel sides, use the similarity of the two triangles formed to relate the sides.