Problem 150. Quadrilateral,
Area, Trisection of Sides.

In the figure below, ABCD is a
quadrilateral of area S. E, F, G, H trisect the sides BC and AD
respectively. If S1 is the area of
quadrilateral EFHG, prove
that:
.
View or post a solution.

Problem 150 on Twitter

@panlepan Vincent. I've found a simple proof (at last!) for this. If we do the same 'across' the figure, we can prove that earlier task 1/2 pic.twitter.com/wkuZwO6zgQ